Expertise of MRCET have researched and collected B.Tech 1st Year Applied Physics & Engineering Chemistry Lab Manual study material in pdf format. This pdf formatted MRCET B.Tech 1st Year Applied Physics & Engineering Chemistry Lab Manual covered the subject concepts in a comprehend manner for easy reference to their students.
CourseB.Tech 1st Year
asd asd Vision & Mission Vision To establish a pedestal for the integral innovation, team spirit, originality and
competence in the students, expose them to face the global challenges and become pioneers of Indian vision of modern society.
Mission To become a model institution in the fields of Engineering, Technology and Management.
To impart holistic education to the students to render them as industry ready engineers.
To ensure synchronization of institute ideologies with challenging demands of International Pioneering Organizations.
PROGRAM OUTCOMES A B.Tech –graduate should possess the following program outcomes.
1 Engineering knowledge: Apply the knowledge of mathematics , science, engineering fundamentals and an engineering specializati on to the solution of complex engineering problems.
2 Problem analysis: Identify ,formulate, review research literature, and analyze comp lex engineering problems reaching substantiated conclusions using first princi ples of mathematics, natural sciences, and engineering sciences.
3 Design/developmen t of solutions: Design solutio ns for complex engineering problems and design system components or processes that meet the specified needs with appropriate consideration for the public health and safety, and the cultur al, societal, and environmental considerations.
4 Conduct investigations of complex problems: Use research-based knowledge and research methods including design of experiments, analysi s and interpretati on of data, and synthesis of the information to provide valid conclusions.
5 Mod ern tool usage: Create, select, and apply appropriat e techniques, resources, and modern engineering and IT tools including prediction and modeling to comp lex engineering activit ies with an understand ing of the limitatio ns.
6 The engineer and society: Apply reasoning infor med by the contextual knowledge to assess societal, health , safet y, legal and cultural issues and the consequent responsibilities relevant to the professional engineering practice .
7 Environment and sustainability: Understand the impact of the professional engineering solutio ns in societal and environmental contexts, and demonstrate the knowledge of, and need for sustainable development.
8 Ethics: Apply ethical principle s and commit to professional ethic s and responsibilities and norms of the engineering practic e.
9 Individual and teamwork: Function effectively as an individual, and as a memb er or leader in diver se teams ,and in multi disciplinary settings.
10 Commun ication: Commu nicate effectively on comp lex engineering activities with the engineering community and with society at large ,such as, being able to comprehend and write effectiv e reports and design documentatio n ,make effective presentatio ns ,and give and receive clear instructions.
11 Project management and finance: Demonstrate knowledge and understa nding of the engineering and management principle s and apply these to one’s own work, as a member and leader in a team, to manage projects and in multi disciplinary environments.
12 Life-long learning: Recognize the need for and have the preparation and ability to engage in independent and life-long learning in the broadest context of technological change.
MALLA REDDY COLLEGE OF ENGINEERING & TECHNOLOGY B. TECH - I- YEAR - I &II -SEM (R22A0082) APPLIED PHYSICS LAB COURSE OBJECTIVES:
1. To experience the mechanical oscillations and resonance phenomena.
2. To verify the concepts of light.
3. To analyze voltage/current phase behavior of RC and LCR circuits.
4. To study the characteristics of semiconductor devices.
5. To understand the concepts of laser .
LIST OF EXPERIMENTS:
1. Melde’s experiment –Frequency of electrical vibrator.
2. Newton’s Rings –Radius of curvature of Plano convex lens.
3. Laser -Wave length of light by using Diffraction grating.
4. CR circuit – Time constant of an RC circuit.
5. LCR Circuit - Quality factor and resonant frequency of LCR circuit.
6. LED -Characteristics of LED.
7. Solar cell -Characteristics of a Solar cell.
8. Optical fiber - Numerical aperture of an optical fiber.
9. Torsional pendulum -Rigidity modulus of given wire (demonstrative).
10. Hall Effect – Hall coefficient of semiconducting samples (demonstrative).
1. Practical physics by Dr. Aparna, Dr K.V Rao, V.G.S.Publications.
2. Engineering physics practical lab manual – MRCET.
1 Students can compare the elastic constants of different metallic wires, and also determine the ac frequency of vibrating bar.
2 Students can illustrate the interference of light phenomena.
3 Wavelength of the given laser can be determined by using diffraction phenomenon 4 By understanding electrical principles, Time constant of RC and resonance phenomenon of LCR circuits can be analyzed.
5 V-I characteristics of various semiconductor devices can be illustrated.
L T P C - - 3 1.5 MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY B. TECH - I- YEAR - I &II -SEM L T P C
- - 3 1.5 (R22A008 2) ENGINEERING CHEMISTRY LAB (Any Eight Experiment s Compulsory) COURSE OBJECTIVES:
The students will be able:
1. To understand and explain scientifically the various chemistry related problems in the industry/engineering and develop experimental skills for building technical competence.
2. To familiarize with the practical implementation of fundamental concepts.
3. To gain hands on experien ce in handling the instruments.
4. To demonstrate the digital and instrumental methods of analysis.
5. To correlate the practical aspects with theoretical concepts.
List of Experiments Titrimetry:
1. Estimation of Hardness of water by EDTA method.
2. Estimation o f Ferrous ion by Dichrometry Instrumental Methods Conductometry:
3. Estimation of concentration of HCl by Conductometric titrations.
4. Estimation of concentration of Acetic acid by Conductometric titrations.
5. Estimation of concentration of HCl by Potentiometric titrations.
6. Estimation of amount of Fe2+ by Potentiometric titration using KMnO 4.
7. Estimation of Copper by Colorimetric method.
Preparation 8. Preparation of a Polymer -Bakelite Physical Property 9. Determination of Surface Tension of a given liquid by Stalagmometer.
Corrosion control method 10. Electroplating of Copper on an Iron object.
1. Inorganic quantitative analysis, Vogel 2. A text book on experiments and calculation in Engineering C hemistry by S.S. Dara Suggested Readings:
1. Practical Engineering Chemistry by K. Mukkanti, etal, B.S. Publications, Hyderabad.
2. Text Book of engineering chemistry by R. N. Goyal and HarrmendraGoel, Ane Books Private Ltd.
The students will be able:
1. To estimate the total hardness present in a sample of water.
2. To know the strength of an acid by conductometric and potentiometric methods.
3. To find the amount of Cu2+ present in unknown sample using colorimetric method.
4. To prepare a thermosett ing polymer.
5. To determine the surface tension of a given liquid.
6. To understand the electroplating method for corrosion protection of metals.
CODE OF CONDUCT 1. Students should bring lab Manual/Record for every laboratory session and should enter the readings/observations in the manual while performing the experiment.
2. The group - wise division made in the beginning should be adhered to, and no mix up of students among different groups will be permitted later.
3. The components required pertaining to t he experiment should be collected from stores in –charge after duly filling in the requisition form.
4. When the experiment is completed, students should disconnect the setup made by them, and should return all the components/instruments taken for the purpose .
5. Any damage to the apparatus that occurs during the experiment should be brought to the notice of lab in -charge, consequently, the cost of repair or new apparatus should be brought by the students.
6. After completion of the experiment, certification of the concerned staff in –charge in the observation book is necessary.
7. Students should be present in the labs for the total scheduled duration.
8. Students should not carry any food items inside the laboratory.
9. Use of cell phones and IPODs are forbidden.
10. Students s hould not write on or deface any lab desks, computers, or any equipment provided to them during the experiment.
11. Every student should keep his/her work area properly before leaving the laboratory.
APPLIED PHYSICS LAB CONTENTS S.NO NAME OF THE EXPERIMENT PAGE NUMBER 1 Melde’s experiment – Frequency of electrical vibrator. 1-6 2 Newton’s Rings – Radius of curvature of Plano convex lens. 7-14
3 Laser - Wave length of light by using Diffraction grating. 15-19 4 CR circuit – Time constant of an RC circuit. 20-27 5 LCR Circuit - Quality factor and resonant frequency of LCR circuit. 28-36 6 LED - Characteristics of LED. 37-41 7 Solar cell - Characteristics of a Solar cell. 42-47
8 Optical fiber - Numerical aperture of an optical fiber. 48-52 9 Torsional pendulum - Rigidity modulus of given wire (demonstrative). 53-60 10 Hall Effect – Hall coefficient of semiconducting samples (demonstrative). 61-68 ENGINEERING CHEMISTRY LAB CONTENTS
S.No NAME OF THE EXPERIMENT PAGE NO.
Common apparatus and terms used i n Chemistry Laboratory 69-75 1 Estimation of Hardness of water by EDTA method 76-83 2 Estimation of Ferrous ion by D ichrometry 84-87 3 Estimation of concentration of HCl by Conductometric T itrations 88-93 4 Estimation of c once ntration of Acetic acid b y Conductometric Titration 94-99
5 Estimation of concentration of HCl by Potentiometric Titrations 100-105 6 Estimation of amount o f Fe2+ by Potentiometric Ti tration using KM no4 106-110 7 Estimation of Copper by Colorimetric m ethod 111-116 8 Preparation of Polymer - Bakelite 117-120 9 Determination of Surface Tension of a given liquid u sing Stalagmometer 121-125
10 Electroplating of Copper on an Iron o bject 126-129 DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 1. MELDE’S EXPERIMENT –FREQUENCY OF ELECTRICAL VIBRATOR.
Aim: To determine the Frequency of a vibrating tuning fork using Melde’s Arrangement.
Apparatus : Connecting wires, Meter scale, thread, pan, weight box, smooth pulley fixed to a stand, electrically maint ained vibrator or a tuning fork, Battery eliminator , EM coil .
1. Longitudinal arrangement : 𝑛= 1√𝑚 √𝑇𝐿 Hz.
2. Transverse arrangement: 𝑛=12√𝑚 √𝑇𝐿 Hz.
Where, m = mass per unit length of the string or Linear density of the thread (gm/cm) L = Length of the single loop (cm) T = Tension in thread.
Note: We know from the formulae, that in the case of longitudinal arrangement it is 1𝐿 while in the case of transverse arrangement it is 12𝐿 Description:
One end of the thin thread is connected to a small screw provided on one of the prongs of the tuning fork, the other end of the thread is connected to a light cardboard pan and the thr ead is passed over a pulley fixed on to a stand kept at a distance of 1 – 2 meters from the
fork. Small weights are placed in the pan so that the sufficient tension is created to the string. The tension in the string can be altered by changing the weights in the pan.
Longitudinal and Transverse vibrations The tuning fork is arranged for longitudinal vibrations as shown in figure i.e., the vibrations of the prong are parallel to the length of the thread. After noting the observations in this
position, the tuning fork is arranged for Transverse vibrations i.e., the vibrations of the prong are perpendicular to the length of the thread. In other words, In transverse wave the prong should vibrate perpendicular to the thread.
1DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Procedure :
1. The apparatus (tuning fork) is first arranged longitudinal vibrations with the length of the string 1 -2 meters and passing over the pulley. The electric circuit is closed and adjusted till the fork vibrates steadily.
2. The load in the pan is adjusted slowly, till a convenient number of loops (say between (3–10) with well – defined nodes and maximum amplitude at the antinodes are formed, the vibrations of the string being in the vertical plan e.
3. The No. of Loops (x) formed in the string between the pulley and the fork is noted. The length of the string between the pulley and the fork (d) is noted.
4. The length (L) of a single loop is calculated by: 𝐿=𝑑𝑥 𝑐𝑚.
5. The experiment is repeated by chan ging the load M. So that the number of loops increased or decreased by one. The readings are tabulated in Table I.
6. Next, the fork or vibrator is arranged for the transverse vibrations as in fig(b). The experiment is repeated as was done for the longitudinal vibrations and the readings are tabulated in table II.
7. At the end of the experiment, the mass m of the pan, the mass of the string ‘w’ and the length ‘y’ of the string are noted.
Mass of the string (w) = --------------- gm Length of the string (y) = -------------- cm Mass of the pan ( 𝑚′) = ------------------ gm Mass per unit length (or) Linear density ‘m’ = ------------------------ gm/cm Table I: Longitudinal Arrangement:
S.No Load Applied in the pan (M) gm Tension T=(𝑀+𝑚′) g No. of
Loops (x) Length of (x) Loops (d) Length
of each Loop 𝐿=𝑑𝑥 √𝑇 √𝑇𝐿
Average value of √𝑇𝐿 2DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in
Table II: Transverse Arrangement :
S. No Load Applied in the pan M gm Tension T = (M+m1) g No. of
Loops (x) Length of x loops (d) Length of
each loop 𝐿=𝑑𝑥 √𝑇 √𝑇𝐿 𝐴𝑣𝑔 𝑜𝑓 √𝑇
𝐿 Precautions :
1. The loops must be well -defined.
2. The plane of vibration of the thread must be vertical.
3. In counting the loop lengths, the two extreme ends must be taken into account.
1. Frequency of a tuning fork in longitudinal arrangement is Hz 2. Frequency of a tuning fork in Transve rse arrangement is Hz .
1. Melde’s experiment helps us understanding the formation of standing waves with nodes and anti nodes.
2. By measuring the distance between nodes and anti nodes are in between nodes and anti nodes the wavelengths can be calculated.
3. With the help of this wavelength and knowing the frequencies the velocity of propagation of the waves can be also determined.
4. In melde’s experiment the vibrations of the electrica lly excited tuning fork can be transmitted as mechanical waves along the thread.
5. We can determine the frequency of elec trically driven Tuning fork in t ransverse longitudinal arrangement.
6. By calculating the sound frequency through this experiment it can ser ve multiple benefits to medical science.
3DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in VIVA VOICE QUESTION AND ANSWERS 1 Define the term frequency. What are the units and dimensional formula of frequency?
Frequency is defined as the number of cycles passing through a fixed point (i.e., oscillations or vibrations or revolutions) per unit time. Frequency is also defined as the number of waves that passes a fixed point in the given time.Its unit is sec -1 or Hertz. Dimensional formula is [𝑀0𝐿0𝑇−1] 2 What are the laws of stretched strings in t erms of frequency?
Frequency is inversely proportional to length of string Frequency is proportional to the root of the tension Frequency is inversely proportional to the root of the linear density of the string.
3 Define Resonance?
When natural freque ncy of a body is equal to applied frequency due to external periodic force then the body executes sympathetic vibrations and the phenomenon is known as resonance.
4 What are longitudinal and transverse waves? Give example for each.
Longitudinal and transverse waves are Mechanical Waves i.e., the waves which propagate through a material medium (mostly gases) at a wave speed which depends on the elastic and inertial properties of that medium. Longitudinal waves are the waves in which t he medium particles vibrate parallel or along the direction of propagation of the wave.
Example: Sound waves in air are longitudinal waves.
Transverse waves are the waves in which the medium particles vibrate perpendicular to the direction of pr opagation of the wave.
Example: Electromagnetic wave; ripple in water and a waves generated on a musical instruments.
5 What are nodes and antinodes?
Region of zero or minimum displacement of wave is called nodes and the region of maximum displacement of wave is called antinodes.
6 What is a Stationary wave?
A stationary wave superposition of incident waves and reflected transverse waves in opposite direction between any two fixed points is known as stationary wave.
7 What is the distance between two consecutive nodes?
The distance between successive nodes (or successive antinodes) is half a wavelength (λ/2).
8 What is the distance between a node and next immediate antinode?
The distance between node and next immediate antinode is quarter of a wavelength (λ/4).
9 What is linear density?
It is defined as the mass per unit length of the thread. Its unit is gm/cm in CGS and kg/m in MKS (or SI).
4DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 5DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
MRCET EAMCET CODE:MLRD www.mrcet.ac.in 6DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 2. NEWTON’S RINGS
Aim: To determine the radius of curvature of Plano convex lens by using Newton’s rings arrangement.
Apparatus : Traveling microscope, sodium vapour lamp, Plano convex lens, a thick glass plate (P 1), a thin glass plate (P 2), a black paper and reading lens.
Radius of curvature of the Plano convex lens 𝑅=𝐷𝑛2−𝐷𝑚24𝜆(𝑛−𝑚) R = Radius of curvature of the Plano convex lens 𝐷𝑛= Diameter of the 𝑛𝑡ℎ ring.
𝐷𝑚= Diameter of the 𝑚𝑡ℎ ring.
𝜆=Wavelength of the light source Description :
A black paper is laid on the base of the traveling microscope over which the thick glass plate 1p is placed. Over this thick glass plate, a Plano convex lens F of large focal length is placed. A parallel beam of light from the sodium lamp is made to fall on the glass plate
2P , inclined at 045 with the hori zontal as shown in the figure 1. A beam of light is reflected on to the large focus lens by the glass plate2P . As a result of interference between the light reflected from the lower surface of the lens and the top surface of the thi ck glass
plate, concentric rings called the Newton’s rings are formed. The observed rings are with alternate bright and dark rings, having a central black spot as seen through the microscope.
7DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Procedure :
1. The point of intersection of the cross -wires in the microscope is brought to the center of the ring system, The wire may be set tangential to any one of the ring; and starting from the centre of the ring system.
2. The microscope is moved on to one side (say ) left across the field of vie w counting the number of rings.
3. After passing beyond 10th or 15th ring, the direction of motion of the microscope is reversed and the cross -wires is set at the 10th or 15th dark ring, tangential to it.
4. The reading on the micro scope scale is noted, using a magnifying glass.
5. Similarly, the readings with the cross -wires is set on 10th, 8th, 6th --- --- --- 2nd dark ring the readings are noted.
6. The microscope is moved in the same direction and the readings corresponding to the 2nd, 4th, 6th --- --- --- 10th, dark ring on right side are noted.
7. Readings are to be noted with the microscope moving in one and the same direction to avoid errors due to backlash.
8. The obser vations are tabulated in table .
A graph is drawn with number of rings as abscissa (x -axis) and the square of diameter of the ring as the ordinate (y -axis). The graph will be a straight line. From graph, the value of (𝐷𝑛2 𝑎𝑚𝑑 𝐷𝑚2 ) corresponding to two numbers 𝒏 𝑎𝑛𝑑 𝒎 are noted . Using these values in equation (2) the radius of curvature is calculated 8
DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 9DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in
1. While taking observations, the microscope should be moved only in one direction to avoid the error due to back -lash.
2. The lens and glass plate must be perfectly clean.
3. The slow motion screw of the microscope must be used while taking readings.
4. The central spot must be dark.
The radius of the curvature of the given Plano convex lens is 𝑹𝒆𝒙𝒑𝒆𝒓𝒊𝒎𝒆𝒏𝒕𝒂𝒍 = ………… cm.
𝑹𝒈𝒓𝒂𝒑𝒉𝒊𝒄𝒂𝒍 = …………… cm.
1. The wavelength of unknown source can be determined.
2. Standardisation of a meter can be done.
3. Optical flatness of surface can be determined.
4. Refractive index of a liquid can be estimated.
10DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in VIVA VOICE QUESTION AND ANSWERS 1 What is the basic principle of Newton’s rings experiment ?
The basic principle illustration of the interference of light waves reflected from the opposite surfaces of a thin film of variable of Newton’s rings experiment is Interference phenomenon in thin films. The phenomenon of Newton’s rings is an thickness.
2 Define Interference ?
It is superposition of two or more coherent waves giving rise for bright and dark fringes of equal width.
3 Why the rings are circul ar ?
The air film formed below the Plano convex lens where the rings are observed, is plano concave. The path difference along the circle is constant that’s why the rings are circular in this experiment 4 What are Newton’s Rings ? Alternate dark and bright r ings with central dark spot are called Newton’s rings.
5 Why it is necessary for the light to fall normally on Plano convex lens ?
In the path difference 2μt Cos r of thin films ,angle of refraction r should be zero(Cos r=1).This is possible only when light rays are made to incident vertically on the air film enclosed, by means of the glass plate kept at 450with respect to the incident beam from the source.
6 What is constructive interference and destructive interference?
When two light waves interfere at e ach other such that the resultant intensity at a point increases due to crest falling on crest or trough falling on the trough. This interference is called constructive interference.
If crest falls on the trough or trough falls on the crest, t here is annihilation or cancellation of the wave. Hence the resultant intensity is zero and it is called destructive interference.
7 What is the purpose of glass plate incline at 𝟒𝟓° in this experiment ?
For normal incidence of light wave.
8 Why the centre of the rings is dark ?
Because the Plano convex lens and the plane glass plate are in contact and corresponding to that particular point of contact the centre ring appears dark.
9 Which light do we use in this experiment ?
Monochromatic light. Example: Sodiu m light, refractive index, radius of curvature of the lens, in designing interferometer.
10 If we replace yellow light with green light, is there any difference in the formation of rings ?
No, because both are monochromatic lights only.
11 What will happen if we use white light in this experiment ?
Colored fringes will form.
11DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 12DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
MRCET EAMCET CODE:MLRD www.mrcet.ac.in 13DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 14
DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 3. WAVE LENGTH OF LASER BEAM Aim: To determine the wavelength of laser beam.
Apparatus: Laser source, Diffraction Grating, Screen and Meter Scale.
Principle: The wavelength of the laser can be determined by using diffraction due to N Slits.
When light rays are incident on a grating a diffraction pattern with intensity maxima will b e observed on the screen with diminishing intensity in various orders.
𝜆=sin𝜃𝑁𝑛 𝐴° Where, ‘’ is the angle of diffraction ‘’ is the wavelength of the laser beam (1 Ao =10-8cm) ‘N’ is the number of lines per cm of the grating . (1 Inch= 2.54 cm )
[For 15000 LPI ‘N’ is 5905.5 /cm and For 2500 LPI ‘N’ is 984.25/cm.] ‘n’ is the order of diffraction.
1 Arrange the laser source and grating on the table at the same height.
2 Focus the laser beam on the grating and observe the diffraction pattern formed on the screen.
3 It will be observed that ce ntral maxima will be of maximum intensity and the other maxima’s are of decreasing intensities. Measure the distance between the screen and grating.
4 Measure the distance between the corresponding maxima of the same order (2x cm).
5 The experiment is repeated for different values of ‘d’ and the readings are noted.
6 The value of wavelength is calculated for each value obtained using the formula 𝐬𝐢𝐧𝜽=𝒙√𝒙𝟐+𝒅𝟐 and the average value of wavelength is determined.
15DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Tabular form:
1. Do not view the laser beam through naked eye.
2. The measurements are to be done accurately.
The wavelength of the laser beam is A0 S No. Distance between screen and grating
(d) cm Order (n) The distance between corresponding maxima (2x)
(cm) 𝒙 cm 𝐬𝐢𝐧𝜽=𝒙√𝒙𝟐+𝒅𝟐 𝜆=sin𝜃
𝑁𝑛 𝑐𝑚 1.
Average 16DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in VIVA VOICE QUESTION AND ANSWERS
1 What is LASER?
The term LASER stands for Light Amplification by Stimulated Emission of Radiation. It is a device which produces a powerful, monochromatic collimated beam of light in which the waves are coherent.
2 What are the characteristic of laser ?
Laser have high i ntensity, high coherence, high monochoromation and high directionality with less divergence.
3 What is the principle of LASER?
The principle of a laser is based on three separate features: a) stimulated emission b) population inversion and c) an optical pum ping.
4 What is diffraction?
Diffraction is the bending or spreading of light through narrow apertures or corners of obstacles and enter into the geometric shadow.
5 What is grating element?
(e+d) is known as grating element where e is the slit width and d is the separation between the two ruled lines or slits.
6 What is wavelength?
The distance between any two successive points in the wave train which have the same phase is called the wavelength.
7 What is monochromatic light?
Light source having single colour or single wavelength or single frequency is called monochromatic light.
8 What is the function of optical resonator?
To amplify or increase the intensity of active medium.
9 What is meta stable state?
Meta stable state is intermediate state and it has a longer lifetime.
10 What is population inversion?
The number of atoms in exited state is more than that of ground state.
17DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 18DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
MRCET EAMCET CODE:MLRD www.mrcet.ac.in 19DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 4. CR CIRCUIT
Aim: To study the growth and decay of current in a C - R Circuit and to determine RC time constant.
Apparatus : C-R circuit board consisting of fixed power supply, Connecting wires, Analog Voltmeter, combinations of Resistor & capacitors, stop clock.
Time constant 𝛕=𝐑×𝐂 seconds .
Where , R is resistance.
C is capacitance.
Current, when passed by keeping key closed CR circuit, current will not reach maximum value immediately. It takes certain time to attain maximum value. Theoretically it is shown that Either CURENT or VOLTAGE or CHARGE. Grows exponentially as per the equation 1 below.
When the key is opened the circuit will be broken. Charge in the condenser discharges. The discharge is also exponentially as per the equa tion 2 below In CR circuit when switch on put on the charge on the condenser (c) grows exponentially as per 𝐐=𝐐𝟎(𝟏−𝐞−𝐭𝐂𝐑⁄)
Where, Q is the charge in time t; and Q 0 is the maximum charge.
The charge grows to maximum value 0.632 of the total charge (Q 0) in t sec. This t, is called time consistent. It depends on product of R & C. Time constant (t) , can be determined by measuring values of R & C as shown in the table I.
Similarly when current is switched off the charge on the conde nser is also discharged as 𝑸=𝑸𝟎𝒆−𝒕𝑪𝑹⁄.
In both the cases of charging and discharging, the equations represent exponential nature as shown in the graphs below.
To study the charge of a capacitor. By charging and discha rging The experiment arrangement for the study of the charging and discharging of a condenser through a resistance is shown in fig. A condenser of capacity C, resistance R, a tap key K are to be connected to a battery B. Connect a voltmeter, V parallel to the co ndenser, by 20
DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in means of which the potential difference across the plates of the condenser can be measured.
Adjust the voltmeter knob so that it reads zero. Switch on the power supply, press the tap key K and simultaneously start a stop clock. When the tap key , K is pressed the current flows and the plates of the condenser get charged. Note the voltmeter reading, V at suitable regula r intervals of time ( say 5 seconds) till the voltage a maximum value 𝑉0 i.e., the condenser gets fully charged. Note the observ ations in table 1. Repeat the experiment for different sets of R
and C values.
21DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Observations :
1. Capacitance (C) = …………………… 𝜇𝐹.
2. Resistance (R) = …………………… k Ω.
Charging Discharging S.No Time (t) sec Voltmeter readings VOLTS S.No Time (t) sec Voltmeter readings
VOLTS 22DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Precautions:
1. In the circuit note that resistance is in 𝑲𝛀 but the capacitance is in 𝝁𝑭. Select the values carefully.
2. Give the connections carefully as per the circuit diagram.
3. Readings should be noted quickly and correctly during charging and discharging.
4. The growth and decay take infinite time interval theoretically. But takes certain time to reach final values practically.
R = C = Time constant ( 𝝉) Charging Discharging Theoretical Graphical 23
DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in VIVA VOICE QUESTION AND ANSWERS 1. What is capacitor?
A capacitor is a device which stores electric energy at very low potential.
2. What is the purpose of Capacitors?
Capacitors are used to store electrical energy to improve the efficiency of electrical gadgets 3. What the resistor will do?
It will oppose the flow of charge.
4. What is Time constant?
It is the time taken for exponential gr owth or decay of charge in an RC circuit. It is known as time constant. It is given by the product of resistance and capacitance of CR -circuit denoted by 𝝉 = RC. The time constant determines nature of the charging and discharging.
5. What is capacitance?
The ratio of magnitude of the charge to the applied voltage of a capacitor.
i.e., Q α V → C = Q/V 6. Define potential?
The electric potential at a point in the electric field is defined as the work done to carry unit charge within the elect ric field.
7. What is the nature of Time Vs Voltage (or current) graph?
Exponentially voltage or charge are increasing during charging and exponential decreasing during discharging of the RC circuit.
8. Describe the types of capacitor?
Non electrolyte capacitors and electrolyte capacitors.
9. Give the unit of capacitor?
Farad 24DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 25
DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 26DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in
27DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 28DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
MRCET EAMCET CODE:MLRD www.mrcet.ac.in 5. L C R SERIES AND PARALLEL RESONANCE CIRCUIT Aim: To study the frequency response of a series and parallel LCR circuits and to determine resonant frequency, band width, and quality factor of the circuit.
Apparatus: LCR Trainer kit, Function Generator and connecting wires.
Band width ∆𝒇=𝒇𝟐−𝒇𝟏 Resonant frequency in series 𝒇𝟎=𝟏𝟐𝝅√𝑳𝑪 Resonant frequency in parallel 𝒇𝟎=𝟏𝟐𝝅√𝑳𝑪
Quality factor , 𝑸=𝒇𝟎𝒇𝟐−𝒇𝟏 Here C is capacitance of the capacitor in Farads ∆𝒇 is Bandwidth of resonant circuit 𝒇𝟎 is the resonant frequency in Hz.
𝒇𝟏 and 𝒇𝟐 are the lower and upper cut off frequencies or half power frequencies in Hz.
LCR in series :
1. Connect the circui t as shown in the circuit diagram.
2. Apply input signal using signal generator. The output should be 10V only.
3. Take the output across the resistor and feed it to Ammeter input sockets.
4. Vary the frequency till the Ammeter records a sharp rise and fall, adjust the signal such that the ammeter deflection is the maximum possible. This is the resonance frequency of the connected combi nation of the circuit.
5. Adjust the signal generator amplitude such that to get full -scale deflection. In Ammeter now reduce the frequency till the deflection falls considerably. Then increase the frequency in regular intervals and note down the Ammeter read ings.
29DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 6. Plot a graph between the current and frequency.
7. Repeat the procedure using different combinations of L,C & R and study how Q is affected.
Also study how resonant frequency depends upon different combinations of L,C, R.
LCR in parallel:
1 Connect the circui t as per the circuit diagram .
2 Apply input signal using signal generator. The output should be 10V only.
3 Take the output acro ss the tank circuit and connected to Ammeter input sockets.
4 Vary the frequency till the Ammeter records a sharp fall, adjust the signal such that the ammeter deflection falls down considerably. Then increase the frequency 5 Adjust the signal generator amplitude such that to get fu ll-scale deflection. N ow reduce the frequency till the deflection falls down considerably. Then increase the frequency in regular intervals and note down the Ammeter readings.
6 Plot a graph between the current and frequency.
7 Repeat the procedure for different values of R and study how Q is affected. Also study how resonant frequency depends upon different combinations of L,C, R.
30DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Table:
Resistance R = ………… Capacitance of capacitor C = ………… Inductance of an inductor L =................
Frequency Current (I) mA Frequency Current (I) mA 31DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in
1. The output voltage of the signal generator should be kept constant for every frequency.
2. The readings should be taken on either side of 𝒇𝟎.
3. R should be less in series circuit and it should be very large in parallel circuit.
4. R should be 10 times the output impedance of the signal generator.
Verified the Reson ant Frequency of LCR in series.
Type of Resonance Resonant frequency 𝒇𝟎=𝟏𝟐𝝅√𝑳𝑪 Band Width ∆𝒇=𝒇𝟐−𝒇𝟏 Quality factor
𝑸=𝒇𝟎∆𝒇 Series Resonance Parallel Resonance Applications:
1. LCR circuit helps in understanding oscillatory discharging or charging of the condenser through L and R.
2. In series circuit maximum current is possible at resonance condition.
3. In parallel LCR circuit voltage is maximum at resonance condition.
4. Using LCR circuit the production of electromagnetic waves can be designed.
5. This is the starting basic point for electro communication engineering.
6. LCR circuit is best example of realizing the electrical resonance process.
7. Analogically mechanical resonance in terms of frequencies or energies can also be realized in mechanically damped oscillation.
VIVA VOICE QUESTION AND ANSWERS 1. What is the purpose of Inductors?
Inductors are also used to store electrical energy but in capacitors the energy is stored in terms of electric fields and in inductors the energy is stored in terms of magnetic fields.
2. What will happen if both capacitor and inductor are connected in a circ uit?
When a capacitor and an inductor are combined in a single circuit the energy can be traded back and forth between them at any given time. This leads to oscillations in the circuit. (e.g.: radio receiver).
3. What is quality factor?
It is the ratio of res onant frequency to the band width.i.e., Q = f 0 / ∆f where ∆𝑓 = (𝑓2 – 𝑓1) is the band width.
The Q, quality factor, of a resonant circuit is a measure of the “goodness” or quality of a resonant circuit. A higher value Q corresponds to a narrower bandw idth, which is desirable in many applications.
32DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 4. What is Bandwidth?
The bandwidth is defined as the difference between the frequencies f 1 and f 2 i.e. ∆𝑓 = (𝑓2 – 𝑓1) 5. What is impedance?
It is the ratio between maximum voltage values to the current value i.e., Z = V max / I . It is the resistance term used in AC circuits 6. What is resonant frequency?
The maximum current or voltage frequency at which inductive reactance and capacitive reactance components are equal in an ac circuit is known as resonant frequency.
7. LCR series circuit is called Acceptor. Why?
Since the series resonant circuit has the lowest possible impedance resonance frequency, thus allowing the AC current to circulate t hrough it.
8. What is the relation between impedance and current in this series circuit?
Inversely proportional 9. What is the status of a current in series and parallel connections?
In LCR series the current is high compared to LCR in parallel where the curre nt is low.
10. What are the types of resonances?
Electrical, electronic, mechanical, magnetic, optical, sound, electron spin resonance (ESR), nuclear magnetic resonance (NMR) etc.
33DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 34DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
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DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 37DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in
6. LED CHARACTERISTICS Aim: To study the V-I characteristics of Light Emitting Diode.
Apparatus : LED characteristic board, Power supply, Analog/ Digital voltmeter and Ammeter, LED & connectors.
LED is an Opto -electronic device which works on the principle of electroluminescence, the process that converts electrical input into a light output. This device basically consists of a direct band gap Semiconductor material doped with impurities to create a structure called p -n junction.
Under forward bias, the positive voltage is applied to the p -region and negative to the n -region. The holes and electrons are pushed towards the junction. The charge carriers that diffuse through p -n junct ion recombine with the majority carriers on the other side and emit photons whose energy is equal to the difference of conduction and valence band of the semiconductor (band gap of semiconductor).
𝐸𝑔=𝐸𝑐−𝐸𝑉=ℎ𝜐 Where, 𝜐 = frequency of emitted ph otons h = plank’s constant .
1. Connect the LED circuit as shown in fig .
2. Slowly increase the forward bias voltage with the help of voltage controller.
3. Note down the corresponding voltage and current readings in the table.
4. Plot a graph between Volt age v/s Current and find forward resistance of diode.
38DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Table :
1. Do not Exceed current limit of 30mA else the laser diode may get damaged.
2. Do not look at the laser directly with the laser turned on.
3. It is extremely damaging to apply a large reverse bias to a laser diode.
V-I Characteristics of LED are studied.
The threshold voltage for gi ven LED is ……… .. V.
1. Sign Applications with LEDs: The low energy consumption , low maintenance, and small size of LEDs have led to uses as status indicators and displays on a variety of equipment and installations.
2. Lighting: The mechanical robustness and long lifetime LEDs are used in automotive lighting on ca rs, motorcycles, and bicycle lights .
3. Data communication and other signaling: Light can be used to transmit data and analog signals. For example, lighting white L EDs can be used in systems assisting people in navigating in closed spaces while searching necessary rooms or objects.
4. Machine vision systems : Barcode scanners are the most common example of machine vision applications, and many of those scanners use red LEDs instead of lasers. Optical computer mice use LEDs as a light source for the miniature camera within the mouse.
5. Biological detection : UV induced fluorescence is one of th e most robust techniques used for rapid real -time detection of biological aerosols.
Sl. No. VOLTAGE (V) CURRENT I (m A) 39DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
MRCET EAMCET CODE:MLRD www.mrcet.ac.in VIVA VOICE QUESTION AND ANSWERS 1 What are the applications of LED ?
LEDs, indicator lamps in electronic devices , traffic signals, digital display, burger alarams etc.
2 What is a LED ?
LED is a Light Emitting Diode which works on the principle of electroluminescence.
3 What is the principle involved behind the emission of light from LEDs ?
Electroluminescence 4 If we increase the LED voltage what happened to LED current ?
LED current increases non -linearly.
5 How is a LED different from other light sources ?
LED consumes less energy and is in toxic compared to incandescent fluorescent light bulbs. It has much longer life time. For example, a 60 -watt incandescent light bulb draws more than $300 worth of electricity per year and provides about 800 lumens of light; an equivalent compact fluorescent uses less than 15 watts and costs only about $75 of electricity per year. LED bulbs are even better, drawing less than 8 watts of
power, costing about $30 per year, and lasting 50,000 hours or longer.
6 What is dynamic resistance ?
Due to the non -linear nature of Current -Voltage curve, there exists a unique value of resistance at every point of the curve which is called dynamic resist ance.
7 What are the materials used in LED ?
GaAs, GaAsP, GaP 40DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 41
DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 42DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in
7. SOLAR CELL CHARACTERISTICS Aim: To determine th e characteristics of solar cell and calculate fill factor.
Apparatus required: Solar cell trainer kit, Solar cell, Variable light source Formula :
Fill factor =𝐼𝑚× 𝑉𝑚𝐼𝑠𝑐× 𝑉𝑜𝑐 Where, 𝐼𝑚is maximum current 𝐼𝑠𝑐 is short circuit current 𝑉𝑚 is maximum voltage 𝑉𝑜𝑐 is open circuit voltage Theory:
If the depletion of unbiased junction is illuminated, charge separation takes place, resulting in forward bias on the junction. Such device having large area junction very close to the surfa ce is capable of delivering power and is known as SOLAR CELL. The cell converts directly solar energy into electricity.
The Solar Cell radiation is proportional to the delivered power of cell. The efficiency of a cell is expressed in terms of the e lectrical power output compared with the power in the incident Photon Flux. The efficiency of Solar Cell depends on the fraction of light reflected from the surface and the fraction absorbed before reaching the junction. Silicon is widely used for Solar Ce lls.
1. Place solar cell directly in front of variable intensity light source, and connect solar cell to trainer kit.
2. Keep constant intensity of variable light source and distance from solar cell to the source.
3. Connect the circuit as shown above .
4. Now measure short circuit current (𝐼𝑠𝑐) for zero load and open circuit voltage (𝑉𝑜𝑐) for maximum load.
5. Vary the load and note down voltage and current readings respectively .
6. Plot a graph by taking voltage and current along x and y axis with the given scale. An exponential power decay curve is obtained.
7. Calculate fill factor.
43DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Table:
S.No Voltage (V) Current (mA) (I) Power 𝑃=𝑉×𝐼
1. Handle apparatus gently.
2. Give connections correctly.
3. The voltage and corresponding current should be noted simultaneously.
Result: V-I characteristics of solar cell were studied.
Fill factor = 44DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Applications:
1. Solar cell for transportation: Solar energy is used in cars. This solar power is created by photovoltaic cells. This electricity is transferred to the storage battery or powers the motor.
2. Solar cell panels: On the rooftop, solar panels are kept. It is used as a solar heater that heats the water. This water can be used for bathing. Also, another use it helps in generating power.
3. Solar thermal power production: Solar thermal power production means the convers ion of solar energy into elec tricity through thermal energy. In this procedure, solar energy is first utili zed to heat up a working fluid, gas, water or any other volatile liquid. This heat energy is then converted into mechanical energy m a turbine. Fina lly, a conven tional generator coupled to a turbine converts this mechanical energy into elec trical energy.
4. Solar charging batteries: Solar charger is a device that uses sunlight to generate electricity. This electricity is then used to charge electrical devices.
5. Solar cells in calculators: Solar -powered calculators use photovoltaic cells. These calculators work with solar energy. The light from the sun gives power for the operation of calculators. Solar calculators work very well in outdoor light.
45DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in VIVA VOICE QUESTION AND ANSWERS 1 What is solar cell?
A solar cell or photovoltaic cell is a device that converts light energy into electrical energy.
2 What is the phenomenon involved in solar cell?
Phenomena involved in solar cell is photo -voltaic effect.
3 Is solar cell prepared from a semiconducting material?
YES, solar cell is Prepared from high semiconductor elements such as gallium, indium, arsenide etc.
4 Write the maximum power output equation ?
Assuming the current/voltage relationship is linear (it's not, but this gives you crude lower bound), you could measure the short -circuit current and the open -cell voltage and do 𝟏𝟒 𝐈𝐕 to obtain the maximum theoretical power given a worst -case 0.25 fill factor.
However a more reasonable value might be obtained by using a different factor 5 Write the equation for the efficiency of solar cell?
The efficiency is the most commonly used parameter to compare the performance of one solar cell to another. Effi ciency is defined as the ratio of energy output from the solar cell to input energy from the sun.
6 What is fill factor?
Fill-factor: The Fill Factor (FF) is essentially a measure of quality of the solar cell. It is calculated by comparing the maximum power to the theoretical power (PT) that would be output at both the open circuit voltage and short circuit current together 7 What are the applications of solar cell ?
Electrica l Grid Power: Solar cell produces electrical power for the commercial grid, solar cells widely used as, many traffic, emergency and construction road signs use solar cells for power, reducing the need for gasoline -powered generators for remote and mobil e uses.
Rooftop Solar Panels: Many commercial and residential buildings have solar panels that produce electricity; in most cases, the building gets its power primarily from a conventional utility connection, but the solar cells generate enough power to re duce the owner’s conventional electric use and the associated electric bill. The solar panel connects to a power management system that automatically switches to the utility when
solar power isn’t available.
46DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 47DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
MRCET EAMCET CODE:MLRD www.mrcet.ac.in 48DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 8. NUMERICAL APERTURE OF AN OPTICAL FIBRE
Aim: To determine the numerical aperture of an optical fib er.
Apparatus: Optical fib er trainer module, NA Jig ( screen with concentric circles ) and screen .
The NA of the optical fiber is =𝑫√𝑫𝟐+𝟒𝑳𝟐 Acceptance angle of an optical fiber 𝜶=𝐬𝐢𝐧−𝟏(𝑵𝑨) Circuit diagram:
Fig: Focusing of light on the circles of given screen (NA jig) Theory :
Optical fiber is a very thin and flexible medium having a cylindrical shape consists of core, cladding and protective shield. The light launched inside the core through its one end propagate s to the other end due to total internal reflection at the core -clad interface. This is the principle of optical fiber. The angle at which the light ray is incident on the fiber such that it is transmitted through the fiber in guided mode is called the “acceptance angle” (maximum
launching angle “α”). The cone defined by twice the acceptance angle is called acceptance cone. The light collecting capacity of the fibre is expressed in terms of acceptance angle using parameter called Numerical Aperture (NA). The Sin of the acceptance angle is called NA of the fibre. Thereby t he NA of an optical system/device is a measure of how much light is collected by system/device.
1. One end of the optical fibre is connected to the power output of LED. And the other end of the fibre is connected to NA Jig through the connector.
2. The AC main is switched on. The light emitted by LED passes through the optical fibre cable to the other end. The set Po knob is adjusted such that, maximum intensity is observed on the screen and it should not be further disturbed.
49DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 3. A screen with concentri c circles of known diameter is moved along the length of the NA Jig to observe the circular spreading of the light intensity on the screen.
4. The screen is adjusted such that, the first circle from the centre of the screen is completely filled with the light . At this position, the distance (L) from this fibre end to the screen is noted on the NA Jig.
5. The experiment is repeated for the subsequent circles by adjusting the length L along NA jig and the readings are noted in table.
S. No Diameter of the circle (D) mm Distance from screen (L) mm 𝐍𝐀 =𝐃√𝐃𝟐+𝟒𝐋𝟐
Acceptance angle 𝜶=𝐬𝐢𝐧−𝟏(𝑵𝑨) Avg values of NA and 𝜶 Precautions:
1. Adjust the distance from the screen properly and measure the diameter of the rings.
2. Handle the optical fibre cable carefully.
3. Use maximum intensity of the light while doing the experiment.
4. Tabulate the readings without parallax Result:
The numerical aperture of the given optical fiber is found to be .
The acceptance angle of the given optical fiber is found to be .
1. NA is generally used in microscopy for describing the acceptance cone.
2. In fiber optics, it describes the angles range where light is occu rring on the fiber optic will be broadcasted along with it.
3. Used in microscope objective.
4. Used in lens, photographic objective.
50DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in VIVA VOICE QUESTION AND ANSWERS 1 What is numerical aperture?
Numerical aperture is thus considered as a light gathering capacity of an optical fibre.
Numerical Aperture is defined as the Sine of half of the angle of fibre's light acceptance cone.
i.e.𝑵𝑨 =𝐬𝐢𝐧𝜶 where, 𝛼 is called acceptance cone angle.
2 What is acceptance angle ?
The acceptance angle of an optical fiber is defined: It is the maximum angle of a ray (against the fiber axis) hitting the fiber core which allows the incident light to be guided by the core.
3 How do you explain total internal reflection ?
When light goes from a denser medium to a less dense medium, as the angle of incidence exceeds the critical angle, the ray reflects back to the denser medium. This phenomenon is called Total Internal Reflection. Total Internal Reflection is a very effi cient reflection, as the loss of light energy is almost negligible. Example: such as glass to air or water to air.
4 Give some lively examples which use total internal reflection ?
Total internal reflection is the operating principle of optical fibers, whic h are used in endoscopes and telecommunications.
5 What is optical fibre ?
An optical fiber is a very thin strand of plastic or glass that is used to transmit messages via light.
6 Mention the types of optical fiber.
Single mode fiber is optical fiber that is designed for the transmission of a single ray or mode of light as a carrier and is used for long -distance signal transmission. Multimode fiber is optical fiber that is designed to carry multiple light rays or modes concurrently, each at a slightly differen t reflection angle within the optical fiber core. Multimode fiber transmission is used for relatively short distances because the modes tend to disperse over longer lengths.
7 What is attenuation?
Attenuation or loss in optical fibers basically refers to the loss of power. During transit, light pulse loses some of their photons, thus reducing their amplitude. Attenuation for a fiber is usually specified in decibels per kilo meter. The degree of attenuation depends on the wavelength of light transmitted.
Attenuation measures the reduction in signal strength by comparing the output power with input power. Measurements are made in decibels (dB). The basic measurement for loss is done by taking the logarithmic ratio of input power (Pi) to the output power (Po).
8 What is bending loss and types of bending loss in optical fibers ?
Transmission loss in the fiber during its propagation through the optical fiber cable.
Types of bending losses in optical fiber are 1. Addition of impurity to fiber.
2. Material composition loss.
3. Absorption & scattering loss.
4. Radiation loss 9 What are the advantages of optical fiber ?
1. Greater bandwidth.2. Low attenuation and greater distance 3. Security 10 What is step index and graded index fiber of an optical fiber?
A step -index prof ile is a refractive index profile characterized by a uniform refractive index within the core and a sharp decrease in refractive index at the core -cladding interface so that 51DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in
the cladding is of a lower refractive index.
In fiber optics, a graded index is a n optical fiber whose core has a refractive index that decreases with increasing radial distance from the optical axis of the fiber.
52DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 53DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
MRCET EAMCET CODE:MLRD www.mrcet.ac.in 9.TORSIONAL PENDULUM Aim: To determine the rigidity modulus (𝜂) of the material of the wire using a Torsional Pendulum.
Apparatus : A circular disc provided with a chuck nut at its center, copper wire, another chuck nut fixed to a wall bracket or a rigid clamp, stop watch, meter s cale, screw gauge, vernier calipers.
Description : The Torsional pendulum consists of a uniform circular metallic disc of about 10 to 12 cm diameter with 1 or 2 cm thickness, suspended by a wire at the center of the disc. The lower end of the wire is gripped into the chuck nut at the center of the disc and the upper end is gripped into another chuck nut, which is fixed to the wall bracket.
η=4πMR2a4×LT2 𝑑𝑦𝑛𝑒𝑠 𝑐𝑚2⁄ Where , M= Mass of the disc (g m) R = Radius of the disc (cm) 𝐿= Length of the wire (cm) 𝑎= Radius of the wire (cm) 𝑇=𝑇𝑖𝑚𝑒 𝑝𝑒𝑟𝑖𝑜𝑑 (sec)
The Wire fixed in between the chuck nuts is twisted using the circular brass disc. When the disc is rotated, the external couple acts on the wire. Due to this an internal couple develops in the wire. Because of these couples similar to action and reaction, the disc starts oscillating about the wire as
axis. The oscillations are known as torsional oscillations.
To determine Rigidity modulus the measurable parameters are M, R, a, L and T. Since the same disc is used M and R can be determined. Here M can be weighed using a balance while R can be measured using vernier calipers as per the ta ble II. The radius of the wire “a” can be determined using
screw guage and can be tabulated in table III. For different length(L), the time periods (T) and T2 are determined and tabulated in the table I. Using the formula substituting all the values, The rigidity modulus can be calculated.
If “a” is the radius of the wire “L” is the length of the wire between the chuck nuts and the Rigidity modulus ("" ) of the material of the wire is related to the couple “C” per unit twist of the w ire as,
𝐶=𝑎4𝜂𝜋2𝐿………..(1) Time period and Torsional Oscillation is related to couple “C” as, 𝑇2=4𝜋2𝐼𝐶………(2)
𝐶=4𝜋2𝐼𝑇2………(3) From equation (3) and (1) we have 𝜂= 8 𝜋𝐼/a4 x 𝐿𝑇2 ………(4)
54DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in The moment of inertia(I) of a circular disc whose geometric axis coincides with the axis of rotation is given by
𝐼=𝑀𝑅22…………(5) where M = Mass of the disc R = Radius of the disc
Substituting the value of “I” from (5) in (4) we get 𝜂=4𝜋𝑀𝑅2𝑎4×𝐿𝑇2…………(6) Procedure:
1. The circular metal disc is suspended as shown in figure. Length of the wire between the chuck nuts is adjusted to 90 cm .
2. When the disc is in equilibrium position, a small mark is made on the curved edge of the disc. This marking will help to note the number of oscillations made by the disc when the disc oscillates.
3. The disc is set to oscillate by slowly turning the disc through a small angle. Care is to be taken to see that there is no lateral movement of the d isc.
4. When the disc is oscillating, the time (t) taken for 10 oscillations is noted with the help of a stopwatch and recorded in the observation table in trial 1.
5. The procedure is repeated for the same length of the wire and again the time taken for 10 osc illations is noted and recorded in the observations table in trial 2 .From trial 1 & 2 the mean for 10 oscillations is obtained. The time period (T) i.e. the time taken for one oscillation is calculated.
6. The experiment is repeated, by decreasing the le ngth of the wire in steps of 10 cm and the results are tabulated in table 1.
7. The radius of the wire ‘a’ is to be found accurately using a screw gauge since it occurs in the fourth power in equation (6).
8. The Radius (r) and the Mass (m) of the disc are found with the vernier calipers and a rough balance respectively. The mean value of (𝐿𝑇2) is substituted in equation (6) and
can be calculated.
9. A graph is drawn by taking ‘L’ on the X - axis and 𝑇2 on Y -axis which repres ent a linear graph. From the linear graph, the slope 𝐿𝑇2 is determined. Using 𝐿𝑇2
the rigidity modulus ‘ 𝜂’ of the wire can be calculated.
55DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Observations:
1. Mass of the disc (M) = ------------- gm 2. Radius of the disc (R) = ------------- cm 3. Average radius of the wire (a) = -------------- cm Table I :
S.No. Length of the wire ‘L’ between the chuck nuts (cm) Time taken for 10 Oscillations
(t sec) Time Period (T sec) 𝑇=𝑡10 𝑇2
𝐿𝑇2 cm/sec2 Trial - I Trial – II Average(t) 1 2
3 4 5 Average value of 𝐿𝑇2⁄ =
Determination of diameter and radius of the disc using Vernier calipers:
𝐿𝑒𝑎𝑠𝑡 𝑐𝑜𝑢𝑛𝑡 𝑜𝑓 𝑉𝑒𝑟𝑛𝑖𝑒𝑟 𝐶𝑎𝑙𝑖𝑝𝑒𝑟𝑠 =𝑉𝑎𝑙𝑢𝑒 𝑜𝑓 𝑜𝑛𝑒 𝑚𝑎𝑖𝑛 𝑠𝑐𝑎𝑙𝑒 𝑑𝑖𝑣𝑖𝑠𝑖𝑜𝑛𝑁𝑜.𝑜𝑓 𝑑𝑖𝑣𝑖𝑠𝑖𝑜𝑛𝑠 𝑜𝑛 𝑣𝑒𝑟𝑛𝑖𝑒𝑟 𝑠𝑐𝑎𝑙𝑒 = ......... 𝑐𝑚 Zero error = ......... Zero correction = .........
S.No. Main Scale Reading (MSR) Vernier Coincidence (n) (n) x L.C Total Reading MSR + (n x L.C) cm Avg
Diameter of the disc = cm Radius of the disc = cm 56DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in
Determination of diameter of the wire using SCREW GUAGE :
𝐿𝑒𝑎𝑠𝑡 𝑐𝑜𝑢𝑛𝑡 =𝑃𝑖𝑡𝑐 ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑐𝑟𝑒𝑤𝑁𝑜.𝑜𝑓 𝐻𝑒𝑎𝑑 𝑠𝑐𝑎𝑙𝑒 𝑑𝑖𝑣𝑖𝑠𝑖𝑜𝑛𝑠 = ………………….𝑚𝑚 Error = Correctio n = S.No Pitch Scale Reading
(PSR) Head Scale Reading H.S.R x. L.C Total reading PSR + (HSR x L.C) mm Observed Corrected 1
2 3 Average diameter Average diameter = mm Radius of the wire (a) = mm………………….cm
1. Ensure the wire is free from kinks.
2. The vibration of the disc must be in the horizontal plane.
3. The amplitude of motion of the disc must be small.
4. Avoid wobbling of the disc.
The rigidity modulus of of the given metallic wire Experimental = dynes/cm2 Graphical = dynes/cm2 Applications:
1. The torsional oscillations will help in determining rigidity moduli or rigidity nature of the material.
2. With help of thee rigidity modulus the other elastic moduli ( Y, Poison ration , 𝜎 ,K) can be estimated.
3. Anybody which can have the torsional oscillations they can be damped. In ballistic galvanometer these oscillations are used in determining charge on the conductor.
4. New researches, promising the determination of frictional for ces between solid surfaces and flowing liquid environments using forced torsion pendulums.
5. Use of a torsional pendulum as a high -pressure gage and determination of viscosity of helium gas at high pressures.
57DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in VIVA VOICE QUESTION AND ANSWERS 1 Define Rigidity modulus? Give the formula & explain ?
It is the ratio of tangential stress to tangential strain. It can also be stated as shearing stress or angular stress to shearing strain or angular strain. It is generally denoted as “η”.
2 On what factors the rigidity modulus (η) depends ?
It depends on nature of solid material, It depends on mass of the material, It depends on radius of disc & depends on length, and inversely on fourth power of radius & finally on square of time period 3 What is Torsional pendulum? Explain in brief ?
A heavy circular metallic disc suspended by means of a wire in between chuck nuts from a rigid support is known as torsional pendulum. The disc is mad e to oscillate about the wire as the axis.
4 Explain need and meaning of the graph.
As per the formula 𝐿𝑇2 is an important term. In this 𝐿 & 𝑇2 are proptional to one another. Hence the graph represents a straight line passing through the origin.
5 How do you show that (η) is constant for a given material ?
𝜂=4𝜋𝑀𝑅2𝑎4×𝐿𝑇2 In the formula 4𝜋𝑀𝑅2𝑎4 is constant. In the second term since L is proportional to 𝑇2 ,
second term is also constant. Finally rigidity modulus η must be definitely a constant 6 If L vs. 𝐓𝟐 is a straight line, what is the nature of the graph between L & T.
L & T is not a straight line but it represents a curve.
7 Write the L.C’s of Vernier and screw gauge.
Least count of Vernier Calipers = 0.01 cm Least count of Screw Gauge = 0.001 cm 8 What is Zero Error and its correction while using screw gauge ?
Zero of Head scale and zero of the Pitch scale if they are not coinciding then there is zero error. If zero is above pitch scale error is negative, must give positive correction by adding & vice -versa.
9 What are the units of η ?
𝑑𝑦𝑛𝑒𝑠 𝑐𝑚2⁄ 10 What are three Elastic Moduli ?
Young’s modulus, rigidity modulus, & bulk modulus.
58DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 59DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
MRCET EAMCET CODE:MLRD www.mrcet.ac.in 60DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 10. HALL EFFECT
Aim: To determine the hall coefficient of the given p type semiconducting material.
Apparatus: IC regulated power supply, Electromagnets, Constant current power supply, Hall sensor & semiconductor crystal.
Hall coefficient 𝑹𝑯=(𝑉𝐻𝐼) 𝑡𝐵𝑚3𝐶⁄ Where, 𝑹𝑯=hall coefficient of semiconductor materials t=thickness of the sample
B=applied magnetic field in the y−direction .
𝑉𝐻=Hall voltage in volts .
𝐼=𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑡ℎ𝑟𝑜𝑢𝑔 ℎ 𝑡ℎ𝑒 𝑠𝑝𝑒𝑐𝑖𝑚𝑎𝑛𝑛 𝑖𝑛 𝑚𝐴 Block diagram of Experimental set up :
61DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Circuit diagram :
Principle: If semiconductor is placed in a uniform magnetic field and a constant current is sent as show in the figure , then a voltage is developed in the sample along z -direction. This voltage is known as hall voltage and the phenomenon is known as Hall effect. The hall voltage is depend on magnetic field and the probe current through the sample.
1 Connect the IC regulated power supply terminals to elect romagnetic coils in their respective sockets.
2 Connect Hall probe to Gauss meter .Switch “ ON” the Gauss meter, set the Gauss meter reading to “0.00” by adjusting the knobs.
3 Now place the Hall probe in the magnetic field exactly at the centre of the electro magnetic cores. Set the Gauss meter reading to 2KG magnetic field. This is achieved by applying suitable current to electromagnets & by simultaneously positioning the electromagnetic cores by turning the knobs.
4 Connect the crystal mounted PCB to constant c urrent power supply to their respective sockets.
5 Remove Hall probe from the magnetic field and place crystal in the same position without disturbing the position of the magnetic cores.
6 Switch “ON” the constant current power supply & apply current in steps of 0.1 Ma, rotate the crystal till it becomes perpendicular to magnetic field. Hall voltage will be maximum in this adjustment, note the corresponding Hall voltage at constant magnetic field.
7 Plot the graph between current and Hall voltage which is a stra ight line & find the slope.
62DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Observations:
Thickness of the sample = 𝟕 ×𝟏𝟎−𝟐 𝑐𝑚 Magnetic flux density B = ...................... KG Tables:
At constant magnetic field S.No Current I (𝑚𝐴) Hall Voltage 𝑉𝐻 (𝑚𝑉) 63
DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in Calculations:
Hall coefficient 𝑅𝐻1=(slope 𝑉𝐻𝐼) 𝑡𝐵 ×108𝑐𝑚3𝑐𝑜𝑙−1 Precautions:
1. Keep the sample perpendicular to the magnetic field.
2. Hall probe must be handled carefully.
3. Do not send the high currents through the electromagnets for longer times.
4. Keep the pole gap of 2.5 cm.
5. When the sample is not placed between the poles, set the initial reading to zero by adjusting the zero control.
Hall coefficient 𝑹𝑯=..............................
1. It is used to find out whether the given semiconductor is N−type or P−type .
2. It is used to measure carrier concentration, mobility and conductivity of a semiconducting material.
3. Hall voltage is produced of two input quantities namely the current and the magnetic field. Using this principle, the Hall effect device is used as a multiplier.
4. It is used as a magnetic field sensor. Using the Hall effect devices, the magnetic field ranging from 𝟏𝝁𝑻 𝑡𝑜𝟏𝑻 is sensed.
64DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in VIVA VOICE QUESTION AND ANSWERS 1 Define Hall Effect?
When a current carrying specimen is placed in a transverse magneticfield then a voltage is developed which is perpendicular to both, direction of current and magnetic field. This phenomenon is known Hall Effect.
2 What causes Hall Effect?
Whenever a charge moves in a mutually perpendicular electric andmagnetic field it experiences Lorentz force due to which it deflects from its path and Hall voltage is developed.
3 what is unit Hall coefficient?
4 Which type of mag net is used in the experiment, temporary or permanent?
5 What is Hall Coefficient?
It is the electric field developed per unit current density per unit magnetic field.
6 What is Lorentz force?
If charge ‘q’ moves in a magnetic and electric field ‘B’ &’E’ respectively with velocity v then force on it is given by F= qE+ Bqv.sin ө 7 What is hall probe ?
A semiconductor sandwiched between two Perspex plates.
8 Under which condition, an electron moving through a magnetic field experiences maximum force ?
An el ectron moving through a magnetic field experiences maximum force, when it moves perpendicular to the direction of the magnetic field.
65DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 66DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB
MRCET EAMCET CODE:MLRD www.mrcet.ac.in 67DEPARTMENT OF HUMANITIES & SCIENCES APPLIED PHYSICS LAB MRCET EAMCET CODE:MLRD www.mrcet.ac.in 68
ENGINEERING CHEMISTRY CODE OF CONDUCT 1. The safe way is the right way to do your job. Plan your work. Follow instructions. If you do not know how to do the experiment safely, ask your laboratory instructor .
2. No one is allowed in the laboratory without the supervision of a laboratory assistant, course instructor, or Supervisor. Perform only authorized experiments, and only in the manner instructed: Do not alter experimental procedures, except as instructed.
3. Laboratory aprons must be worn at all times.
4. Close-toed shoes must be worn at all times.
5. It is strongly recommended that you wear clothing that completely covers your arms, legs, and feet while working in the laboratory. Inadequate protection often leads to injury. Avoid wearing expensive clothing to lab as it may get damaged.
6. Absolutely NO food or drinks are allowed into the laboratory.
7. All accidents, injuries, explosions, or fires must be reported at once to the laboratory instructor.
8. Horseplay and carelessness are not permitted. Do not run in labor atory areas.
9. If you see a colleague doing something dangerous, point it out to him or her and to the laboratory instructor.
10. Report to your laboratory instructor all unsafe conditions, unsafe acts, and "near misses" that might cause future accidents. Repo rt any accident or fire, no matter how trivial, to the laboratory instructor.
11. Maintain your working area in a reasonable state of neatness. Clean off your lab work bench before leaving the laboratory.
DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in COMMON APPARATUS AND TERMS USED IN CHEMISTRY LABORATORY EXPERIMENTS Pipettes : Pipettes permit the transfer of accurately known volumes from one container to another.
Commonly we use volumetric pipettes Burettes : Burettes like measuring pipettes make it possible to deliver any volume up to the maximum capacity of the device. A burette consists of a ca librated tube to hold titrant and a valve arrangement by which the flow of titrant i s controlled.
Volumetric Flask : Volumetric flasks are manufactured with capacities ranging from 5ml to 5 liter and are usually calibrated to contain a specific volume when filled in line etched on the neck.
They are used for the preparation of standard s olution and for dilution of samples to a fixed volume prior to taking aliquots with pipettes.
The Burette Stand Standard Flask : The flask filled with standard solution known as standard flask.
Titrations : Titrations are widely used in analytical chemist ry to determine the concentration of acids, bases, proteins, metal ions, oxidants, reductants and many other species. Titrations are based on a reaction between the analyte and a standard reagent known as “TITRANT”. Titrimetry includes a group of analytica l methods that are based on determining the quantity of a reagent of known concentration that is required to react completely with the analyte. Volumetric titrimetry is
a type of titrimetry in which the volume of a standard r eagent is the measured quantita tively.
Titration :The process of finding out the volume of one of the solution required to react completely with a definite volume of other solution of known concentration is a called as titration.
Titrant: The solution of known strength is called titrant Titrate: The solution which contains the substance to be estimated Standard Solution : A solution of known concentration that is exactly used in titrimetry is known as “standard solution”.
Equivalence Point : It is the point in a titration when the amount of added standard reagent is exactly equivalent to the amount of analyte. The end point at which physical changes occurs is known as equivalence point End Point : It is the point which indicates the com pletion of reaction Titration Error : The difference in volume (or) mass between the equivalence point and the end
point is the titration error.
Indicator s: Indicators are added to the analyte solution to produce an observable change at near equivalence p oint. Large changes in the relative concentration of analyte (or) titrant occur in the equivalence point region. These concentrations changes cause the indicator to change in 69DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB
MRCET E AMCET CODE: MLRD www.mrcet.ac.in appearance. During titration, the titrant is added to the flask, with swirling un til the colour of the indicator persists.
Primary Standard : Any substance stable, pure, readily soluble in water, with high equivalent weight and the composition of its solution should not change on standing or during storage is called primary standard and it serves as the reference material for a titrimetric method of analysis.
For example crystalline oxalic acid, potassium dichromate and anhydrous sodium carbonate etc.
are the primary standard substances.
Secondary Standard : The substance which do not fulfill the requirements of primary standard, their solutions are not directly prepared by weighing and the exact strength of the solution is found by titrating it again st some primary standard is called secondary standard and the process is called standardization .
For example: NaOH, KOH which are hygroscopic, KMnO 4which undergoes auto decomposition in permanganate solution on standing and inorganic acids like HCl, H 2SO 4 whose concentrations are known approximately.
Volumetric Calculations : For expressing the concentrations of the solu tions MOLARITY and NORMALITY are usually employed.
(a)Molarity : The number of moles of solute present in 1 liter of the solution is known as “MOLARITY”.
(b)Normality : The number of gram equivalent weights of the s olute present in one liter of the solution is known as the Normality of the solution. Normality of the solution is denoted by ‘N’.
Calculation of the Molarity of Solution : If ‘n’ be the number of moles of solute and ‘V’ be the liters of solution then Mo larity is given by VnM Where WMWn.
Where W is the weight of solute in grams, M.W is the gram molecular weight of the solute.
VXWMWM1. Calculation of Normality of Solution : If ‘n’ gm equivalent weight of solute is dissolved in ‘V’ liters of the solution, then the normality of the solution is given by VnN
But WEWn. E.W is the gram equivalent weight of the solute.
70DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in Hence VXWEWN1
. For example, what is the molarity of 25.5 grams of NaCl dissolved in water, total vo lume of the solution being 100 mL?
First calculate molecular weight of the solute, NaCl. Recall that the atomic mass on the periodic table is the same number as how much a mole of the substance would weigh, in grams. So:
Na: 23.0 g/mol Cl: 35.5 g/mol therefore NaCl: 58.5 g/mol Write down what you are given in grams and convert into moles.
25.5 g x1 mol = mol 58.5 g = 0.436 mol This 0.436 mol is dissolved in 100. mL, so:
100. mL x 1 L = L 1000mL = 0.100 L now set up the fraction so it is in terms of mol/L:
0.436 mol = M 0.100 L 4.36 mol = 4.36 M L Example 2: Prepare 800 mL of 2 M sodium chloride
Mwt NaCl = 58.5 g/mol (The molecular weight or molar mass of NaCl) Volume in ml x ml to L x Molarity x Molecular weight= grams needed 800 ml x 1 L x 2 mol x 58.5 g = g of NaCl needed 1000 mL mol 93.6 g of NaCl is needed; bring the total volume up to 800 mL.
Example 3: Dilution with molarity :
M1V1 = M2V2 or CiVi = CfVf M1 = starting molarity M2 = ending molarity C= concentration V1 = starting volume V2 = ending volume i = initial f = final In this equation, the volume goes with its molarity on the same side of the equals sign.
71DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in Prepare 100 mL of 1.0 M hydrochloric acid from concentrated, 12.1 M, hydrochloric acid.
So to solve this problem, you would put 100 mL and 1.0 M on the same side of the equals sign because they go together. 12.1 M would go with a variable on the other side of the equals sign.
We need to figure out how much of the really concentrated acid we need to only have 100 mL of a 1.0 M solution of acid.
M1V1 = M2V2 (12.1 M) V 1 = (1.0 M)(100 mL) divide both sides by 12.1 M V1 = 8.26 mL of concentrated HCl Molality, m :
Number of moles of solute divided by the number of kilograms of SOLVENT (not of solution.) Note for water, 1 kg of solvent is 1L.
To make a liter of a molal solution with water, you would add one liter of water because 1 L of water weighs 1 kg.
The difference between molar and molal is that when making 1 liter of a solution, with molar, the total volume is 1 liter, whereas with molal the tot al volume is slightly larger than 1 liter because you added 1 liter of water to the solute. It is a small difference, but for some reason chemists think it is important.
Normality, N The number of equivalents of solute per liter of solution.
For example , 1 M HCl is 1 N, but 1 M H 2SO 4 is 2 N because 2 hydrogen ions are given off per mole of H 2SO 4.
I’ve only seen normality used in reference to acids and bases. Essentially it is the number of hydrogens that can come off in solution as the acid dissociates .
So, a 3 M H 2SO 4 solution would be 6 N 3 mol x 2 H+ ions released = 6 equivalents of H+ ions being released = 6 N L mole liter The equivalent weight or the molecular weight expressed in grams is called gram equivalent weight or gram molecular weight.
1) Equivalent weight of an acid = Molecular wt of an acidNo.of replaceable hydrogen atoms in one molecule of acid 72DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB
MRCET E AMCET CODE: MLRD www.mrcet.ac.in 2) Equivalent weight of base = Molecular wt of base No.of replaceable OH−groups in one molecule of base Example:
The equivalent weight of HCl is 36.5/1 = 36.5 The equivalent weight of H 2SO 4 is 98/2 = 49 The equivalent weight of oxalic acid is 126/2 = 63 The equivalent weight of NaOH is 40/1 = 40 The equivalent weight of Ca(OH) 2 is 74/2 = 37
3) Equivalent weight of oxidising / reducing agents = Molecular mass/ Number of electrons lost or gained in the redox reaction ) Examples:
a) Potassium dichromate (K 2Cr2O7) oxidizes Cr2O72-+14 H+ + 6e- 2Cr 3+ + 7H 2O Hence its equivalent wt = 294/6 = 49 b) Potassium permanganate (KM nO4) oxidizes MnO 22- + 8H+ + 5e- Mn2+ + 4H 2O
Hence its equivalent weight = 158/5 = 31.6 Types Of Titrations a) Permanganometric Titrations : The titrations involving addition of potassium permanganate as a standard reagent to the analyte whose titer value is to be determined are kno wn as Permanganometric titrations.
Ex: Preparation of standard solution of oxalic acid and estimate the amount of ferrous iron by Permanganometric titrations KMnO 4 is a powerful oxidizing agent and in acidic medium, it oxidizes oxalic acid to CO 2 2KMnO 4 + 3H 2SO 4 + 5H 2C2O4 K2SO 4 + 2MnSO 4 + 8H 2O + 10CO 2 Here KMnO 4 acts as a self indicator
(b) Potassium Dichromate titrations : The titration s involving the addition of Potassium Dichromate as a standard reagent to the analyte whose titer value is to be determined are known are known as Potassium Dichromate titrations Potassium Dichromate is a strong oxidizing agent in acidic medium and i t is used for estimation of many reducing salts especially of ferrous salts. Here Di -phenyl amine is used as
an indicator 73DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in (c) Conductometric Titrations : The titrations involving the addition of standard reagent from
the burette to the analyte present in the conductivity cell involving the change in the conductance of the analyte with the addition of the standard reagent. Conductometric titrations are those in which the conductance can be determined with the help of conductivity measurements. While carryin g out the conductometric titrations, the following apparatus are to be used.
(i) Thermostat ii) Conductivity cell (iii) Conductivity water (iv) Conductivity meter.
The conductance of each volume should be correct ed for dilution using the formula.
C’= C (V+µ) V Where C‘= corrected conductance C = observed conductance V= initial volume of solution in a beaker
µ = volume of titrating solution added Conductance : The reciprocal of resistance is known as conductance. It is denoted by ‘C’.
C=1/R The unit for conductance is mho.
Conductance Curve :
(a) The curve which is drawn between the volume of the solution added in ml & c orrected conductance C’ is known as “conductance curve”.
For ex: - (1) for strong acid vs. strong base the conductance curve is given by (b) Conductance curve of mixture of acids vs. strong base is given by 74DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in
Potentiometric Titrations : A Potentiometric titration involves measurement of the potential of a suitable electrode (indicator) as a function of titrant volume. While carrying out the Potentiometric titrations the following apparatus are to be used.
(a) Potentiometer (b) Magnetic stirrer (c) Calomel electrode (d) Pipette (e) Burette
Potentiometric titrations offer additional advantages over potentiometry as the measurement is based on the titrant volume that causes a rap id change in potential near the equivalence point for detecting end point.
Potentiometric Curve : A graph is drawn between EMF and the volume of the titrant added near the endpoint 0.1ml portions of the titrant is added each time and measure. The sudden i ncrement in the EMF values indicated as end point . From the graphs the concentrations are calculated.
These graphs are called “Potentiometric titrations curves”. For example Potentiometric curve of strong acid vs. strong base is shown by 75DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in
1. ESTIMATION OF HARDNESS OF WATER BY EDTA METHOD AIM: To determine the total, permanent and temporary hardness of water by EDTA method.
APPARATUS : Burette, Conical flask, Pipette and beakers.
CHEMICALS : Standard ZnSO 4 solution , EDTA Solution, Ammonia –ammonium chloride buffer and water sample .
INDICATOR : Eriochrome black –T END POINT: The end point is noted when the colour of the solution changes from wine red to blue.
PRINCIPLE: The hardness of water is due to the presence of salts of Ca2+and Mg2+. The bicarbonates of Ca2+and Mg2+ impart temporary hardness to water which can be removed by boiling. The amount of Ca2+ and Mg2+ is estimated by complexometric method using EDTA. The obtained value gives the total hardness. The permanent hardness is determined first by precipitating the bicarbonates of Ca2+and Mg2+ by heating and filtering off and the filtrate is
titrated with EDTA. The temporary hardness is obtained by subtracting permanent hardness from total hardness.
EDTA Titratio ns (or complex ometric titrations): The titrations involving EDTA as a complexing agent are known as “EDTA Titrations” (or) “Complex Formation Titrations ”.
EDTA stands for ‘ Ethylene Di -amino Tetra Acetic acid ” or “Di-amino Ethane Tetra Acetic Acid .
The structure of EDTA is given by EDTA forms complexes with metal ions like Ca2+, Mg2+, Ba2+, and Sr2+ in aqueous solution.
Complexometric t itration is the titration of metal ion with a reagent, usually EDTA, which forms chelated complex with a met al.
76DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in The common indicator used is Erichrome Black -T Indicator (EBT), at the end point the colour generally changes from wine red to blue.
Ethylene diamine tetra acetic acid [EDTA] forms colorless stable complex with Ca+2 and Mg+2 ions present in water at pH 9-10. To maintain pH of the solution at 9-10, NH 3-NH 4Cl buffer solution is used. Eriochrome black –T (EBT) is used as indicator. The hard water when treated with (EBT) in presence of buffer solution forms unstable wine red colo r complex with Ca+2 and Mg+2 ions present in water.
The stability of a metal indicator complex is less than that of metal EDTA complex. Hence during the titration EDTA extracts the metal ions from the metal ion EBT indicato r complex and forms stable color less metal EDTA complex releasing free indicator. Hence the end point of the titration is the co lor change from wine red to blue color.
77DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in Eriochrome -Black T (EBT indicator) Metal -EDTA complex PROCEDURE:
PART A: STANDARDISATION OF EDTA SOLUTION 10ml of standard Zn2+solution is pipette out into a well cleaned conical flask. To it one drop of indicator and 1 ml of buffer are added, then the solution is titrated against EDTA until wine red color changes from wine red to blue. This is taken as end point. Titrations are repeated until two successively concurrent values are obtained. The molarity of EDTA is calculated using
the formula M1V1=M2V2 PART B: DETERMINATION OF TOTAL HARDNESS OF TAP WATER 50ml of tap water is taken into a well cleaned conical flask. To it 2ml of buffer and 2 -3 drops of EBT indicator are added. The color of resulting solution is wine red. The contents of the conical flask are titrated against EDTA which is taken in the b urette until the color of the solution
changes from wine red to blue. This is the end point. Repeat the titration until two successively concurrent values are obtained The molarity of tap water is calculated using the formula M 2V2=M 3V3 and the total hardness is calculated using amount of Ca2+ × M.W of CaCO 3×103.
78DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in OBSERVATION:
PART A: STANDARDISATION OF EDTA SOLUTION S.NO Volume of standard Zn+2 solution (ml) Burette readings Initial Final Volume of EDTA run down ‘x’ ml
1. 10 0 2. 10 0 M1V1=M 2V2 M1= Molarity of standard Zn2 +solution 0.05N 1V
= Volume of standard Zn2 +solution 10ml 2V Volume of EDTA rundown M2= Molarity of EDTA Solution PART B: DETERMINATION OF TOTAL HARDNESS OF TAP WATER
S.NO Volume of tap water (ml) Burette readings (ml) Initial Final Volume of EDTA run down ‘x’ ml 1. 50 0
2. 50 0 M2V2=M 3V3 M2= Molarity of EDTA solution 2V= Volume of EDTA rundown
M3= Molarity of tap water V3= Volume of tap water .
79DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in The total hardness of tap water = Amount of Ca2+ × M.W of CaCO 3×103ppm DETERMINATION OF PERMANENT HARDNESS OF WATER
Place 250ml of water sample in a 500ml beaker and boil gently for 20 -30 minutes. Cool and filter, collect the filtrate into a 250ml standard flask. Make up the solution to the mark by adding distilled water and shake the solution well. Pipette out 50ml of this made up solution into a clean conical flask, which has been rinsed with distilled water. Add 2ml of p H = 10 buffer solution and 2 to 3 drops of EBT indicator. Titrate this solution against the standard EDTA solution until the
colour changes from wine red to blue. Note down the reading, repeat the process to get at least two equal titer values. Calculate the permanent and then temporary hardness as parts per million of CaCO 3.
PART C: DETERMINATION OF PERMANENT HARDNESS OF TAP WATER S.NO Volume of boiled water (ml) Burette readings (ml) Initial Final Volume of EDTA run
down ‘x’ ml 1. 50 0 2. 50 0 EDTA BOILED WATER M2 = calculated in 1ststep M 4 = ?
V2 = burette reading V 4 = 50 ml n2 = 1 n4 = 1 80DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in
Amount of Ca2+present in water sample = M4 × M.W of Ca+2 × Vol of EDTA 1000 The permanent hardness of tap water = Amount of Ca2+ × M.W of CaCO 3 × 103 ppm Temporary hardness = Total hardness – Permanent hardness RESULT:
1. Total hardness of the given water sample= ---------- ppm 2. Permanent hardness of the given water sample= -------- ppm 3. Temporary hardness of the given water sample= -------- ppm VIVA QUESTIONS:
1. Which reagent is used to determine hardness of water EDTA is used as a regent to determine hardness of water 2. What is the difference between hard water and soft water.
The water which does not give lat her readily with soap is hard water and the water which readily gives much lather with soap is soft water.
3. What is the cause of hardness of water.
It is due the presence of bicarbonates, chlorides and sulphates of calcium and magnesium in water.
4. How is hardness in water classified Hardness in water is classified as (1) Temporary hardness and (2) permanent hardness.
5. What is the difference between temporary and permanent hardness.
Temporary hardness is due to unstable bicarbonates of Ca and Mg, while permanent hardness is due to more stable Cl- and SO 42- of Ca and Mg.
6. How is temporary hardness removed The temporary hardness of water can be removed by boiling water during which bicarbonates decompose to give carbonates.
81DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 7. What is EDTA.
EDTA is ethylene diamine tetra acetic acid.
8. Why is disodium salt of EDTA preferred to EDTA EDTA is sparingly soluble in water. Its disodium salt is more soluble as it is ionisable and hence it is preferred.
9. What is a buffer solution.
The solution which resists change in its pH value even after adding small amount of an acid or a base to it is called a buffer solution.
10. Which buffer solution is added and why it is added during the determination of hardness of water.
NH 3-NH 4Cl buffer solution is added to maintain PH around 9 -10 to form stable metal EDTA complex.
11. Name the most commonly employed indicator in EDTA titrations and what is the end point of titration Indicator used is Eriochrome Black T. End point of the titration is color changes from wine red to blue color 12. What is the application of hardness dat a in env ironmental engineering practice
a) Hardness of water is an important consideration in determining the suitability of water for domestic and industrial uses.
b) Determination of hardness serves as a basic for routine control of softening processes.
13. What are Complexometric titrations.
Titrations which involve the formation of soluble, undissociated, stoichiometric complex at the equivalence point are called complexometric titrations.
14. What are the units of hardness 1. ppm (parts per million) 2. Degree Clarke 3. Degree French 4. mg/l
15. Does EDTA remove hardness from water.
No, EDTA does not remove hardness but it only determines the hardness of water .
82DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in NOTES/CALCULATIONS 83
DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 2. ESTIMATION OF FERROUS ION BY DICHROMETRY AIM: To estimate the amount of ferrous ion (Fe+2) present in a given solution using standard Potassium dichromate.
APPARATUS: Beakers, conical flask, burette, pipette, measuring jar.
CHEMICALS REQUIRED : K2Cr2O7, Mohr’s salt, Conc.H 2SO 4, conc.H 3PO 4 INDICATOR: Diphenyl amine END POINT: Colorless to blue-violet PRINCIPLE: Potassium dichromate, K2Cr2O7, is an inorganic chemical reagent, most commonly used as an oxidizing agent. In acidic medium K2Cr2O7 oxidizes the ferrous ion (Fe+2) to ferric ion
(Fe+3). The completion of the oxidation reaction is marked by appearance of blue-violet color.
K2Cr2O7 + 6FeSO 4 + 7H 2SO 4 K2SO 4 + Cr 2 (SO 4)3 + 3Fe2 (SO 4)3 + 7H 2O PROCEDURE:
Preparation of Standard ( K2Cr2O7) solution:
i) Weigh out accurately the given pure crystalline samp le of potassium dichromate and transfer into 100 ml standard (volumetric) flask provided with a funnel.
ii) Dissolve the dichromate in a small quantity of distilled water, a nd make up to the mark. The contents in the flask are shaken well for uniform concentration.
iii) Calculate the normality of potassium dichromate.
W1 = Weight of bottle + substance (K 2Cr2O7) = gms W2 = Weight of bottle = gms Weight of substance (K 2Cr2O7) = (W1 -W2) = gms.
Normality of the K 2Cr2O7 solution = (W1-W2) X 10 / Equivalent Weight N = (W1-W2) X 10 / 49 = Estimation of Ferrous Ion (Fe2+) 1. Pipette out 10mL the given unknown ferrous solution into a clean conical flask.
2. To it add 2mL of conc. H 2SO 4, 2mL of Conc. H 3PO 4 and 2drops of Diphenyl amine indicator.
Shake the contents well.
84DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 3. Fill the burette with the standard K 2Cr2O7 solution.
4. Titrate the contents of conical flask with the K2Cr2O7 solution till the color of the solution turns blue-violet.
5. Repeat the titration to get concurrent readings.
OBSERVATIONS AND CALCULATIONS:
Estimation of Ferrous Ion (Fe+2):
S.NO Volume of unknown Fe+2 sol.
(mL) Burette reading Volume of K2Cr2O7 run down (mL) Initial ( mL) Final (mL)
1. 10 2. 10 CALCULATIONS:
N1 = Normality of K 2Cr2O7 solution = N2 = Normality of Ferrous iron solution = V1 = Volume of K 2Cr2O7 solution = V2 = Volume of Ferrous iron solution = 20 ml N1V1 = N 2 V2
N2 = N 1 V1 / V2 Normality of Ferrous iron solution = N 2 = N 1 V1/V2 Amount of Ferrous iron present in the whole of the given solution (100 ml) = N 2 X 55.85/10 RESULT:
Amount of Ferrous iron present in the whole of the given solution (100 ml) = gm.
1. Define Morality. Give its formula.
2. Name the indicator used in this experiment?
3. What type of titration is involved in this experiment?
4. What are the molecular and equivalent weights of K2Cr2O 7?
85DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 5. Write the chemical reactions involved in this experiment?
6. What is the equivalent weight of iron in this experiment?
7. What is the equivalent ratio of K2Cr2O7 and FeSO 4?
8. What is Oxidation?
9. What is Reduction?
10. Why do you observe a green colour before the end point?
11. How do you detect the end point?
12. Define an oxidizing and a reducing agent.
13. What are oxidizing & reducing agents in this experiment?
86DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in NOTES/CALCULATIONS 87
DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in Instrumental M ethods Conductometry 3. ESTIMATION OF CONCENTRATION OF HCl BY
CONDUCTOMETRIC TITRATION AIM: To determine the neutralization point in an acid base titration and strength of HCl by titrating with NaOH using conductivity meter.
APPARATUS : Conductivity meter , Conduct ivity Cell, Burette, Beaker and Glass Rod.
CHEMICALS : HCl solution , 1 N NaOH and distilled water.
PRINCIPLE: As the alkali is added from the burette into the beaker containing acid, the concentration of H+ ions change in a graphical manner, which leads to a considerable change in the electrical conductance of the solution, which is measured using a conductivity m eter. Then from the plot of conductance versus volume of alkali, the precise neutralization point is determined. The titration of strong acid verses strong base involves the following equation.
In the titration of HCl against NaOH, initially the conducta nce of HCl solution is maximum due to complete ionization . As the alkali is added, the conductance of solution decreases and after the neutralization point the conductance starts increasing. This is because during addition of alkali, the fast moving H+ ions are replaced by slow moving Na+ ions, hence conductance decreases.
Once the neutralization point is reached, addition of alkali introduces fast moving OH- ions, there by increasing the conductivity of the solution.
PROCEDURE: Pipette out 200ml of HCl into a clean 250ml be aker. Fill the burette with 1 M NaOH solution. Di p a conductivity cell in the HCl solution and connect it to the conductivity meter and note the initial conductance of solution. Run down the NaOH solution from the burette in small vol umes of 1ml and 0.5ml at the end point to be expected in to the cell and note the conductance.
GRAPH: A plot of conductance on Y -axis versus volume of alkali on X -axis is drawn.
Extrapolate the straight lines and note the neutralization point from the gr aph.
88DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in OBSERVATION :
S.NO. Volume of NaOH (ml) Conductance (µs) 1 0 2. 1 3. 2 4. 3
5. 4 6. 5 7. 6 8. 7 9. 8
10. 9 11. 10 12 11 13. 12 14. 13
15. 14 16. 15 17. 16 18. 17 19. 18
20. 19 21. 20 89DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in
Experimental diagram for C onductometric Titrations:
N1V1 = N 2V2 Where N 1= Strength of the a cid =?
V1 = Volume of acid taken in the beaker = 200 ml N2= Strength of alkali = 1N V2= Volume of alkali from the graph.
Normality of HCl = Volume of NaOH (equivalence point) X Normality of NaOH Volume of HCl taken = ………………….. N RESULT:
1. From the graph the volume of NaOH required for the neutraliza tion of HCl is ----------- ml 2. The Normality of HCl by titrating with NaOH using conductometer is …………. N 90DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in
VIVA QUESTIONS :
1. What is meant by conductometric titration Titrations involving conductivity measurements of electrolytes to get endpoint are called conductometric titrations.
2. Define conductance and give its units.
It is a measure of ability of a material to carry electric current. For direct current, conductanc e is called conductivity and is equal to 1/R, where R is the resistance of the material. For alternating current, conductance is called admittance . Conductance is measured in mhos.
3. Why the conductance at first decreases and then increases during the titration Conductance decreases initially because the fast moving H+ ions are replaced by slow moving OH- ions on titrating with NaOH and it again increases after the end point due to the increase in OH- ion concentration.
4. Explain why equivalent conductivity increases with dilution.
The equivalent and molar conductance increases with dilution because these are the products of specific conductance and volume of the solution containing 1 g equivalent of the electrolyte. (λ eq= K x V) . Hence they are directly proportional to volume.
5. Why specific conductance decreases with dilution.
Conductance of solution increases with increase in the number of ions, charge on the ions and mobility of ions. Specific conductance is the conductance offered by unit vol ume of an electrolyte. So when dilution increases number of ions present in the unit volume of an electrolyte decreases, so specific conductance decreases.
6. Write down the equation involved in the titration of strong acid vs. strong base.
7. What is the en d point in this titrations.
End point or neutralization point is the point at which all H+ ions reacts with OH- ions to form salt or the lowest possible conductance that can be observed for a titration is known as end point of that titration .
8. What are the factors that influence the conducta nce of an electrolytic solution.
Charge of the ion, mobility of the ion and number of ions.
9. What are the advantages of conduct metric titrations over volumetric titrations .
1. Colored solutions where no indicator is found can be successfully titrated by this method.
2. This method is more useful for titration of weak acid against weak base, where no indicators are available in volumetric analysis.
3. More accurate r esults are obtained because; the end point is obtained from the graph.
91DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in NOTES/CALCULATIONS 92
DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 93DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in
4. ESTIMATION OF CONCENTRATION OF ACETIC ACID BY CONDUCTOMETRIC TITRATION AIM: To determine the neutralization point and concentration of acetic acid by conduct ometric titration.
APPARATUS: Conductivity meter , Conductivity Cell, Burette, Beaker and Glass Rod.
CHEMICALS : CH 3COOH solution, 1 N NaOH and distilled water.
PRINCIPLE: Solution of electrolytes conducts electricity due to te presence of ions. The specific conductance of a solution is proportional to the concentration of ions in it. The titration of acetic acid of verses NaOH involves the following equation .
(salt, strong electrolyte) When a solution of acetic acid is titrated with NaOH, the fast moving hydrogen ions are progressively replaced by slow moving sodium ions. Init ially the conductivity of CH 3COOH is low, this is due to the poor dissociatio n of CH 3COOH. As NaOH is added g radually, conductance increases slowly. This is due to the formation of highly ionized CH 3COONa. Finally the
conductivity rises rapidly as the alka li is introduced in excess after the neutralization of the weak acid.
Prepare 0. 1N CH 3COOH , and 1N NaOH solutions and take them in separate beakers . Fill the micro -burette with 1N NaOH solution. Place the conductivity cell in distilled water an d adjust the display to 1.000 with calibration knob. Take a beaker and add 20ml of CH 3COOH . Dip a conductivity cell in the CH 3COOH solution and connect it to the conductivity meter and note the initial conductance of solution. Run down the NaOH solution f rom the burette in small volumes
of 1ml and 0.5ml at the end point to be expected in to the cell and note the conductance.
The conductivity increases slowly upto the end point. After the end point , on further addition of NaOH will suddenly increases the conductivity.
94DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in GRAPH: A plot of conductance on Y -axis versus volume of alkali on X -axis is drawn.
Extrapolate the straight lines and note the neutralization point from the graph.
Observations a nd Graph:
S.NO. Volume of NaOH (ml) Conductance (µs) 1 0 2. 1 3. 2 4. 3
5. 4 6. 5 7. 6 8. 7 9. 8
10. 9 11. 10 12 11 13. 12 14. 13
15. 14 16. 15 17. 16 18. 17 19. 18
20. 19 21. 20 95DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in
N1V1 = N 2V2 Where N 1= Strength of acetic acid =?
V1 = Volume of acetic acid taken in the beaker = 20 ml N2= Strength of NaOH = 1N V2= Volume of NaOH required for the neutralization of acetic acid from the graph , Normality of CH 3COOH = Volume of NaOH (V 2) X Normality of NaOH Volume of Acetic Acid
= ………………….. N RESULT:
1. Volume of NaOH required for neutralization of weak acid (CH 3COOH), = ----- ml.
2. The Normality of CH 3COOH by titrating with NaOH using conductometer is …………. N .
96DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in VIVA QUESTIONS :
1. Define conductance and give its units.
It is a measure of ability of a material to carry electric current. For direct current, conductance is called conduc tivity and is equal to 1/R, where R is the resistance of the material. For alternating current, conductance is called admittance . Conductance is measured in mhos.
2. Give the examples of strong electrolytes and weak electrolytes.
Examples for a stro ng electrolyte are HCl, H 2SO 4, NaOH, H 3PO 4 etc.
Examples for weak electrolytes are H 2CO 3, CH 3COOH, NH 4OH etc.
3. Explain the graph for the titration of weak acid vs strong base 4. Write down the equation involved in the titration of weak acid vs strong base.
5. Can we use conducto metric titrations for the determination of equivalence point of tribasic acid .
Yes tribasic acids like H 3PO 4 (orthophosphoric acid) c onductance can be determined by conductometry. In this case three endpoints are obtained.
6. What is the species present at the neutralisation point.
CH 3COONa is present at theneutralization point.
97DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in NOTES/CALCULATIONS 98
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Potentiometry 5. ESTIMATION OF CONCENTRATION OF HCl BY POTENTIOMETRIC TITRATION AIM: To determine the equivalence point between strong acid a nd strong base and normality of HCl by titrating with NaOH using potentiometer.
APPARATUS : Potentiometer , saturated calomel electrode, quinhydrone electrode, b eaker, burette and stirrer.
CHEMICALS: HCl, 0.1N NaOH, quinhydrone powder and distilled water.
When a solution of strong acid (HCl) is titrated with the solution of a strong base (NaOH), the change in PH will be reflected in the change in EMF . When a small amount of alkali is added to the acid, a little change in the EMF is produced in the beginning. This change in electrode potential depends upon the fraction of hydrogen ion s removed. As an equivalence point reaches, the fraction of the hydrogen ions removed by constant volume of stan dard alkali increases
rapidly, th ereby causing a rapid change in the EMF. Thus if the EMF of the cell is plotted against the volume of the stand ard alkali added, a curve is obtained. As the changes in EMF is much more rapid near the equivalent point, the exact equivalent point is obtained by differential method where, a graph of ΔE/ΔV vs v olume of alkali added, gives the maximum of the curve which corresponds to equivalence point of the titration.
The cell can be represented as Pt / Q, QH 2 / H+= ? // KCl (saturated solution)(s) / Hg2Cl2 /Hg (s), Cell EMF = E cathode - E anode PROCEDURE: Pipette out 20ml of HCl solution into 100ml beaker and saturate it with quinhydrone powder and dip the indicator electrode (platinum electrode), connect the indicator
electrode and saturated calomel ele ctrode (reference electrode) to the potentiometer. The two half Ecell = 0.2415 - E0-2.303 RTlog H+F100DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB
MRCET E AMCET CODE: MLRD www.mrcet.ac.in cells are connec ted by means of a salt bridge. The potentiometer is standardized and the used fo r measuring the emf directly. 0.1N NaOH is taken in the burette and is added to the HCl solutio n.
Measure the emf of the acid taken in the beaker initially. First carry out t he rough titrations by adding 1 ml of NaOH and measure the emf for each addition. The emf increase gradually and then shows a sudden increase in the emf. Take enough readings a fter the sudden increase in emf.
From these rough titrations, the range of end point is determined.
After finding the end point range, fair titrations are car ried out by repeatedly adding 1 ml of NaOH as before and near the end point, small additions in the form of 0.1ml is added and emf is measured for each addition and the readings are tabulated.
Graph is plotted with volume o f alkali (Na OH) along X -axis and measured emf along Y -axis. A sigmoid curve is obtained and the equiva lence point is noted at the point of intersection.
To obtain a sharp end point, another graph of volume of alkali (NaOH) along X -axis and ΔE/ΔV along Y -axis is plotted. The maximum obtained in the curve gives the accurate equivalence point.
101DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in CALCULATION:
N1V1 = N 2V2 Where N 1= Strength of the Acid =?
V1 = Volume of acid taken in the beaker = 20ml N2= Strength of alkali = 0.1N V2= Volume of alkali from the graph.
Normality of H Cl = Volume of NaOH (equivalence point) X Normality of NaOH Volume of HCl taken (20ml) = ………………….. N OBSERVATION:
S. No Volume of NaOH (ml) EMF (mV) 1 1 2 2 3 3
4 4 5 5 6 6 7 7 8 8
9 9 10 10 11 11 12 12 13 13
14 14 15 15 16 16 17 17 18 18
19 19 20 20 102DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in
3. The equivalence point of potentiometric titra tion between strong acid v s strong base is ……………. ml 4. The Normality of HCl by titrating with NaOH using potentiometer is …………. N VIVA QUESTIONS:
1. Define electrode potential.
It is a measure of tendency of a metallic electrode to lose or gain electrons when it is in contact with its own ions in solution.
2. What is EMF.
The difference of potentials between the electrodes of a cell which causes flow of current from an electrode at higher potential to other electrode at lower potential is known as electromotive force or cell potential.
5. Define a reference electrode .
The electrode of standard potential, with which we can compare the potentials of and other electrode is called a reference electrode. The best reference electrode used is standard hydrogen electrodes. The electrode potentials at all temp is taken as zero.
4. Why salt bridge is used in the construction of a cell .
Salt bridge helps to complete the circuit by allowing the ions to flow from one solution to the other without mixing the two solutions.
It helps to maintain electrical neutrality of the solution in the half cells.
5. What are potentiometric t itrations The potentiometric titrations are those titrations which involve the measurement of electrode potentials with the addition of the titrant. The end point is detected by measuring the changes in the potential of a suitable electrode during t he course of reaction. No indicator is used in this titrations. The end point of the reaction is indicated by a sharp change in the potential of
6. What are the Electrodes used in potentiometric titrations Calomel electrode, Glass electrode , Ion-selective electrodes , Silver indicating electrodes , Mercury -coated indicating electrodes , Platinum redox electrodes 7. What is an indicator electrode The electrode whose potential varies during the reac tion and which depends upon the
concentration of ionic species is called indicator electrode.
103DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in NOTES/CALCULATIONS 104
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6. ESTIMATION OF AMOUNT OF Fe2+ BY POTENTIOMETRIC TITRATION USING KMnO 4 AIM : To estimate the amount of fer rous ion present in a given ferrous solution by potentiometric titration .
APPARATUS: Potentiometer, Pt -electrode , Calomel electrode, Burette , Beaker , Pipette and Stirrer .
CHEMICALS: FeSO 4 solution, KMnO 4 solution and H 2SO 4.
PRINCIPLE : Potentiometric titrations depend on measurement of emf between reference electrode and an indicator electrode. When a solution of ferrous iron is titrated with a solution of potassium perma nganate, the following redox reaction takes place.
5Fe2+ + MnO4- + 8H+ → 5Fe3+ + Mn2+ + 4H 2O During this titration Fe2+ is converted in to Fe3+, whose concentration increases. At the end point, there will be a sharp change due to sudden removal of all Fe2+ ions. The cell is set up by connecting this redox electrode with a c alomel electrode as shown below.
Hg, Hg 2Cl2, KCl (saturated) // Fe2+, Fe3+/Pt Cell EMF = E Cathode - EAnode A graph between emf measured against the volume of potassium perma nganate added is drawn and the end point is noted from the graph.
PROCEDURE 10ml of f errous sulphate solution is pipette o ut into a 100 ml beaker and add 3 -4 drops of dil.H 2SO 4 (10% solution) . A platinum electrode and a calomel electrode are dipped into this solution and conn ected to a potentiometer. Then 1 ml of potassium permanganate is added to the solution from the burette and stirred well for 30 seconds. The emf is measured and the titration is
continued by ad ding potassium permanganate in 1 ml increments till five measurements after the end point.
Ecell = 0.77+0.05921logFe3+Fe2+- 0.2415106DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB
MRCET E AMCET CODE: MLRD www.mrcet.ac.in A graph is drawn by plotting the emf against the volume of potassium permanganate and the end point range is fixed. The strength of f errous solution is calculated from the end point.
S.No. Volume of KMnO 4 (ml) EMF (mV ) 1 0 2 1 3 2 4 3
5 4 6 5 7 6 8 7 9 8
10 9 11 10 12 11 13 12 14 13
15 14 MODEL GRAPH 1.
Volume of KMnO4End PointEMF (mV)End PointVolume of KMnO4E/ V107
DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in CALCULATIONS :
M1V1𝑛1=M2V2𝑛2 Molarity of Ferrous sulphate (M1) = ?
Volume of Ferrous sulphate (V2) = 10 ml Number of moles of Fe2+ (n1) = 5 Molarity of Potassium permanganate (M 2) = 0.02M Volume of Potassium permanganate (V2) =……. ml (End point ) Number of moles of MnO 4 (n2) = 1
M1 x 105=0.02 x end point1 M1=0.02 x end point x 510
1. The volume of KMnO 4 required to oxidized Fe2+ ions (ferrous ions) into Fe3+ions (ferric ions) is ……….ml.
2. The strength of ferrous ions in FeSO 4 solution is …….. M VIVA QUESTIONS:
1. Which electrodes are used in this potentiometric titration.
Calomel and Redox electrode (Pt / Fe2+, Fe3+) 2. Which oxidizing agent is used in this potentiometric titration.
KMnO 4 is used as oxidizing agent.
3. Write Nernst equation for cell reaction.
4. What is the role of H 2SO 4.
It initiates and reduces KMnO 4.
5. Name the type of titration involved in the titration of Fe2+ vs KMnO 4.
6. Which electrode act as indicator electrode in this titration.
Pt / Fe2+, Fe3+.
Ecell = 0.77+0.05921logFe3+Fe2+- 0.2415108DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB
MRCET E AMCET CODE: MLRD www.mrcet.ac.in NOTES/CALCULATIONS 109DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in
110DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in Colorimetry 7. ESTIMATION OF COPPER BY COLORIMETRIC METHOD
AIM: Estimation of Copper in the given sample by Colorimetry APPARATUS: Colorimeter, Cuvettes, Volumetric flasks and beakers CHEMICALS: Copper sulphate, Water, Test solution PRINCIPLE: Colorimeter measures the optical density of an absorbing substance where optical densit y (O.D) is defined as O.D =
log 1oII Where oI = Intensity of incident light I = Intensity of transmitted light
As per beers law, optical density of an absorbing substance is related to the concentration by the equation.
. . .O D E C l . ( . ). 2O D E l CWhere ‘C’ is the concentration of the substance, l is the path length, which represents the width of the cell used and is constant for a give n cell used, E is the molar absorption coefficient and is a constant for given substance. Equation (2) may be written as
C 3 Equation (3) represents the quantitative form of Beer’s law. If the optica l density of a substance is determined at varying concentration. A plot of O.D.vs C gives a straight line.
111DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in PROCEDURE :
1. Calibrate the instrument by proper selection of the filter in colorimeter.
2. Place a glass cuve tte containing distilled water in to the colorimeter ho le and select the filter No. (40) and set the instrument for 100% transmittance (i.e., at Zero).
3. Then take 0.1M CuSO 4 solution into another cuvet te, wipe out the outer surface of the cuvette and place it in the colorimeter. Note the absorbance which is displayed on the instrument.
4. Repeat the procedure for all the other filters (i.e., at 45, 47, 51, 52 , 54, 57, 60, 67) and note the readings. The filter No. which gives the maximum absorbance is selected and again place the cuvette with distilled water and adjust to 100% transmittance.
5. After selecting the proper filter, different concentrations of the given CuSO 4 solution are made as follows.
6. Measure the absorbance for each concentration and tabulate the r eadings.
7. Plot a graph by taking absorbance along Y -axis and concentration along X -axis. A straight line passing through the origin is obtained.
8. The slope of the curve gives the molar extinction coefficient of the given CuSO 4 solution.
Estimation of Unknown CuSO 4 Solution Fill the colorimeter cuvet te with the given unknown CuSO 4 solution and note the absorbance.
This absorbance is marked on the calibration curve from which the concentration of the given unknown CuSO 4 solution is obtained.
Colorimeter Cuvette Volume of CuSO 4 (ml) 1 2 3 4 5 6 7 8 9 10 Volume of H 2O (ml) 9 8 7 6 5 4 3 2 1 0 112DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB
MRCET E AMCET CODE: MLRD www.mrcet.ac.in CALCULATIONS & TABULATION:
Step1: Selection of Filter:
Filter No % Absorbance 45 47 51 52
54 57 60 67 Step 2:
Volume of CuSO 4 (ml) Volume of H 2O (ml) Concentration of CuSO 4 (mg/L ) Absorbance 1 9 0.01
2 8 0.02 3 7 0.03 4 6 0.04 5 5 0.05 6 4 0.06
7 3 0.07 8 2 0.08 9 1 0.09 10 0 0.1 Unknown
Standard calibration graph RESULT:
The concentration of the given unknown CuSO 4 solution was found to be --------------- .
XYConcentration of CuSO4Absorbance113DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB
MRCET E AMCET CODE: MLRD www.mrcet.ac.in VIVA QUESTIONS:
1. On which principle does the colorimeter works.
The colorim eter works on the principle of Beer –lamberts law 2. What is meant by c olorimetry.
The study of variation in the intensity of a given coloured compound with change in concentr ation of the compound is termed as colorimetric analysis.
3. Explain Lamberts –Beers law.
The decrease in intensity of incident light is proportional to the thickness of absorbing medium and the concentration of solution. Mathematical expression of the law is given as 0 lg o AICLI Where Io = intensity of incident light I = intensity of transmitted light
A = absorbance L = thickness of the medium C = concentration in mol L -1 ε = molar absorption coefficient 114
DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in NOTES/CALCULATIONS 115DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB
MRCET E AMCET CODE: MLRD www.mrcet.ac.in 48 116DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 49 Preparation
8. PREPARATION OF POLYMER - BAKELITE AIM : To pre pare phenol formaldehyde resin (Bakelite) .
CHEMICAL S: Glacial acetic acid, 40% formaldehyde solution, Phenol, conc. H 2SO 4 APPARATUS REQUIRED : Glass rod, beakers, funnel, measuring cylinder, dropper and filter paper.
PRINCIPLE: Phenol formaldehyde resins (PFs) are condensation polymers and are obtained by condensing phenol with formaldehyde in the presence of an acidic or alkaline catalyst. They were first prepared by Bakeland , an American Chemist who gave them the name as Bakelite.
These are thermosetting polymers.
THERMOSETS : The polymers which on heating change irreversibly into hard rigid and infusible materials are called thermosetting polymers. These polymers are usually prepared by heating relatively low molecular mass, semi fluid polymers, which becomes infusible and form an insoluble hard mass on heating. The hardening on heating is due to the formation of extensive cross -linking between different polymeric chains. Thi s lead to the formation of a 3 -Dimensional
network of bonds connecting the polymer chains. Since the 3D network structure is rigid and does not soften on heating, the thermosetting polymers cannot be reprocessed. Some important examples of thermosetting po lymers are Urea -Formaldehyde resin and Melamine -Formaldehyde resins.
Phenol - formaldehyde resins having low degree of polymerization are soft. They possess excellent adhesive properties and are usually used as bonding glue for laminated wooden planks and in varnishes and lacquers.
Phenol - formaldehyde resins having high degree of polymerization are hard, rigid, scratch resistant and infusible. They are resistant to non -oxidizing acids, salts and many organic solvents. They can withstand very hi gh temperatures. They act as excellent electrical insulators also.
117DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 50 Uses:
They are used for making molded articles such as radio and TV parts, combs, fountain pen barrels, phonograph records etc.
They are used for making decorative laminates, wall coverin gs etc.
They are used for making electrical goods such as switches, plugs etc.
They are used for impregnating fabrics wood and paper.
They a re used as binding glue for laminated wooden planks and in varnishes and Lacquers.
Sulphonated phenol -formaldehyde resins are use as ion -exchange resins.
PREPARATION: PFs are prepared by reaction of phenol with formaldehyde in the presence of acidic or basic catalyst. The process may be carried out as follows :
A mixture of phenol and formaldehyde are allowed to react in the presence of a catalyst. The process involves formation of methylene bridges in ortho , para or both ortho and para positions.
This results first in the formation of linear polymer (Called NOVALAC ) and then in to cross -linked polymer called phenol -formaldehyde resin or Bakelite.
118DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 51 PROCEDURE:
1. Place 5ml of glacial acetic acid and 2.5ml of 40% formaldehyde solution in a 500ml beaker and add 2 grams of phenol.
2. Add few ml of conc. s ulphuric acid into the mixture carefully. Within 5 min. a large mass of plastic is formed.
3. The residue obtained is washed several times with distilled water, and filtered product is dried and y ield is calculated.
RESULT: The weight of the p henol formaldehyde resin is -------------- g.
The reaction is sometimes vigorous and it is better to be a few feet away from the beaker while adding the H 2SO 4 and until the reaction is complete.
The experiment should be preferably carried out in fume cupboard.
1. What is the other name given for Phenol formaldehyde?
Phenol formaldehyde is also known as Bakelite 2. What are the monomers used for preparation of bakelite.
Monomers used for preparation of bakelite are Phenol and Formaldehyde 3. Give main uses of the phenol formaldehyde resin.
1. They are used for making moulded articles suc h as radio and TV parts, combs.
2. They are used for making decorative laminates, wall coverings etc.
3. They are used for making electrical goods such as switches, plugs etc.
4. They are used for impregnating fabrics wood and paper.
5. They a re used as binding glue for laminated wooden planks, in varnishes and Lacquers.
4. What type of co -polymer is phenol formaldehyde resin?
It is a thermosetting polymer .
5. What are thermosetting polymers The polymers which on heating change irreversibly into hard rigid and infusible Materials are called thermosetting polymers.
6. Briefly describe the properties of phenol resins .
Hard, rigid, scratch r esistant and infusible. Resistant to non -oxidizing acids, salts and many organic solvents. They can withstand very high temperatures. They act as excellent electrical insulators.
119DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 52 NOTES/CALCULATIONS 120
DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 53 Physical Properties 9. DETERMINATION OF SURFACE TENSION OF A GIVEN LIQUID BY STALAGMOMETER
AIM: To determine the surfa ce tension of a given liquid using s talagmometer.
APPARATUS: Stalagmometer, Specifi c gravity bottle, Rubber bulb and Analytical balance CHEMICALS: Distilled water and Methanol (or) Ethanol PRINCIPLE:
Surface tensi on is the characteristic propert y of every liquid and it is due to intermolecular attraction among molecules of liquid. A molecule in the interior part of the liquid is attracted by the surroundi ng molecules in all directions and hence resultant force on the molecule is zero, whereas the molecules on the surface of the liquid are attrac ted only towards the interior i.e., sides and the bottom are in const ant tension due to the
downward flow of the molecules in bulk, this tension at the surface is known as surface tension. It is defined as the force in dynes acting on a surface at right an gles to any line of unit length. It is denoted by “ γ” (gamma) and its units are dynes/cm.
Table given below lists the surface tension of several liquids at 200C.
Liquid Surface tension (dynes/cm) Liquid Surface tension (dynes/cm) Water 72.8 Ethylene glycol 47.7 Benzene 28.9 Glycerol 63.4
Toluene 28.4 Carbon tetrachloride 27.0 Acetone 23.7 Ethyl iodide 29.9 Methyl alcohol 22.6 Ethyl bromide 24.2 Ethyl alcohol 22.3 Nitrobenzene 41.8 PROCEDURE
The determination of surface tension of a liquid involves the following 2 steps.
DETERMINATION OF DENSITY OF A LIQUID Density of a liquid is mass/unit volume . It is found by using specific gravity bottles. The specific gravity bottle is first washed with distilled water and finally with alcohol and 121DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB
MRCET E AMCET CODE: MLRD www.mrcet.ac.in 54 dried . The weight of the empty specific gravity bottle is found by using analytical balance. Let it beW 1gm. Then it is filled with the distilled water and its weight is accurately determined. Let it be W 2 gm. Now the given unknown liquid is then filled in the s pecific gravity bottles and the weight i s found. Let this weight be W 3gm, the density
of the unknown liquid (d 2) is calculated as:
Density of liquid (d2) = Weight of liquid Weight of water × Density of water DETERMINATION OF SUR FACE TENSION OF A GIVEN LIQUID :
The stal agmometer is first washed thoroughly with distilled water and finally with little alcohol and dried. A clean rubber tube is attached to the upper end of the stalagmometer. A screw pitch cork is fixed on the rubber tube to regulat e the flow of liquid by lifting the influx of air.
The stal agmometer is dipped in a beaker of water and suck the water till it rises above the upper mark (X). I n the stal agmometer the water level is carefully brought to the mark (X) . The pitch cork is opened in such a way that it allows the flow of 12 -18 drops per minute. Now the stal agmometer is adjusted.
Then water is sucked above the mark and the no of drops of water that flows from the mark (X) to the mark (Y) are noted. This is rep eated 3 to 4 times with water.
Now the stal agmometer is rinsed with the liquid whose surface tension is to be determined. The liquid is then filled in the stal agmometer as above and no. of drops that flow from the mark(X) to mark (Y) is noted. This is repe ated 3 or 4 times with the liquid and the experimental results are noted in the tabular form.
Stalagmometer 122DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 55 CALC ULATIONS:
Calculation of density of the liquid Room temperature = 27oC Weight of empty specific gravity bottle (W 1) = Weight of specific gravity bottle + water (W 2) = Weigh t of specific gravity bottle + g iven liquid (W 3) =
Weight of water = (W 2-W1) = Weight of given liquid = (W 3-W1) = Density of water (d 1) = 1 gm/cc Density of liquid (d2) = Weight of liquidWeight of water × Density of water
S. No. Volume of water + Volume of liquid Solution (ml) Concentration
of liquid solution Number of drops Surface tension (dynes/cm) Exp.1 Exp. 2 Average
(N) 1 50 + 0 Pure water 2 50 + 50 0.5% Therefore the surface tension of given liquid (γ 2) is determined busing the following equation.
𝛾2 = 𝑛1𝑑2𝑛2𝑑1 × 𝛾1 Where γ1 = Surface tension of water=72.8 dynes/cm n1= no. of drops of water
d1= density of water γ 2= surface tension of given liquid n2= no. of drops of given liquid d2= density of given liquid RESULT :
The surface tension of given test liquid γ2 = …………… dynes/cm 123DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 56 VIVA QUESTIONS:
1. Define surface tension.
The tangential cohesive force acting along the unit le ngth of the surface of a liquid.
T = F / L Where F = total force along a line L = length of the line 2. What are units of surface tension in C.G.S. and S.I. (M.K.S.) system
Dynes / cm (C.G.S.) Newton / meter (M.K.S.) 3. What are cohesion and adhesion force.
Cohesion force is the attractive force between like molecules, whereas, the adhesion is the attractive force between unlike molecules, e.g. attraction between glass slide and the liquid.
4. What are the factor s affecting the surface tension a) Nature of liquid b) Na ture of the surface in contact c) Temperature 5. What is the effect of tem perature on the surface tension .
Surface tension decreases with the rise of temperature.
6. Which instrument is used to find out the su rface tension of a given liquid Stalagmometer is an instrument by which surface tension of a liquid is determined.
7. What is the value of surface tension of water.
72.8 dyne/cm 8. Is surface tension an intensive or extensive property.
Surface tension is an intensive property.
124DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 57 NOTES/CALCULATIONS :
125DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 58 Corrosion Control Method 10. ELECTROPLATING OF COPPER ON AN IRON OBJECT
AIM : Electroplating of copper on an iron object.
cathode - a key or a steel spoon a copper strip --anode electronic balance battery or power source (9 -12 V) DC insulated wire leads with alligator clips at both end
Beaker CHEMICALS : electrolytic solution – approx. 50 mL of 2.0 mol/L CuSO 4 PRINCIPLE:
The process of depositing a layer of one metal over the surface of another metal by passing electric current is called elec troplating. Electroplating of metals is done to protect them from corrosion and for decoration purpose. For example, the vessels of iron are electroplated with copper or silver or gold to make it attractive and to protect from rusting.
Copper is a soft, ductile metal used in numerous industrial processes and applications. Copper's excellent thermal properties and high electrical conductivity make it a top choice for manufacturing products such as wire and cab le, integrated circuits and circuit boards , conducto rs, electric motors, building materials, piping and many other items. Aside from making cheap jewelry, electroplating has important
uses in the automotive industry for chrome plating, and in the electronics industry for optics and sensors. Many common obje cts such as tin cans are actually electroplated steel with a protective layer of tin.
Medical science has experimented with electroplating to create synthetic joints with electroplated coatings, and new advances in electronics have been made with electrop lated materials.
126DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 59 PROCEDURE:
To deposit a layer of copper metal on an iron object, take a glass beaker and fill it with copper sulphate solution (electrolyte). Connect the plate of copper metal to the positive terminal (anode) of battery and iron object to the negative terminal (cathode) of the battery. Now, dip these two electrodes in the solution of copper sulphate. When an electric current is passed through the CuSO 4 solution, a thin layer of copper metal is
deposited on the cathode (iron o bject) and an equivalent amount of copper is lost by the anode (copper plate) and is dissolved into the solution.
A copper -plated key will be prepared using the electroplating technique. In the preparation of the copper -plated key, positive Cu2+ ions from the electrolyte bath will become attracted to a key carrying a negative charge. When the Cu2+ ions reach the key they will gain electrons and become reduced to form solid copper on its surface:
Cu2+ (aq) + 2e- → Cu(s) The copper (II) ions remove d from the bath must be replenished; this is accomplished at the anode where a solid copper strip undergoes oxidation:
Cu(s) → Cu2+ (aq) + 2e- 127DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 60 OBSERVATION
RESULT : Amount of copper deposited on Iron Key --------------- mg VIVA QUESTIONS:
1. What is electroplating?
The process of depositing a layer of one metal over the surface of another metal by passing electric current is called electroplating.
2. How to obtain a smooth and firm metal layer on the electroplated object?
a) Temperature, pH and concentration of ions in the electrolyte should be kept constant.
b) Oil dirt on the surface of electroplated object should be removed before electroplating.
c) Low current and voltage is used 3. How can electroplating be d one?
Electroplating involves passing an electric current throu gh a solution called an electrolyte. This is done by dipping two terminals called electrodes into the electrolyte and connecting them into a circuit with a battery or other power supply.
4. What is electroplating used f or?
Electroplating is widely used in various industries for coating metal objects with a thin layer of a different metal. The layer of metal deposited has some desired property, which the metal of the object lacks. ... Electroplating has wide usage in industries. It is also used in making ine xpensive jewelry.
5. How Electroplating Works?
Electroplating works like a galvanic cell in reverse. An electrical current reduces cations from a solution so that they can coat a conductive material with a thin layer.
6. What are the engineering applications of electroplating?
Engineers can plate copper onto a variety of surfaces for use in the automotive, aerospace, electrical, or defense industries. Because copper is a soft, highly malleable metal with excellent electrical and thermal conductivity, it is the perfect substance for a variety of use cases . However, sometimes a harder surface may be required. In these instances, copper
plating can be used to increase surface strength. Item mass before electroplating mass after electroplating difference in mass Iron Key ------ mg ------ mg ------ mg Copper sheet ------ mg ------ mg ------ mg
128DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 61 NOTES/CALCUL ATIONS 129
DEPARTMENT OF HUMANITIES & SCIENCES ENGINEERING CHEMISTRY LAB MRCET E AMCET CODE: MLRD www.mrcet.ac.in 62 130