SATHYABAMA UNIVERSITY (Established Under Section 3 of UGC Act, 1956) Jeppiaar Nagar, Rajiv Gandhi road, Chennai

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SATHYABAMA UNIVERSITY (Established Under Section 3 of UGC Act, 1956) Jeppiaar Nagar, Rajiv Gandhi road, Chennai 600 119 DEPARTMENT OF CHEMISTRY I SEMESTER

1 SATHYABAMA UNIVERSITY (Established Under Section 3 of UGC Act, 1956) Jeppiaar Nagar, Rajiv Gandhi road, Chennai DEPARTMENT OF CHEMISTRY I SEMESTER / II SEMESTER Subject Name: Engineering Chemistry Lab Subject code: SCY4051 LAB MANUAL (Common to ALL Branches) Name : Year : Branch and Section Roll No. :

2 GENERAL INSTRUCTIONS Students will not be allowed for the practical classes without lab coat, shoes, lab manual, observation book and record note book. Students should maintain their observation note book and record note book neatly. Both the record and observation note book should be covered with brown sheet. Students should write the date, name of the expt., diagram, tabulation, procedure, etc. in their observation note book before entering the lab. Students should write the completed experiment in the record note book, only after getting it corrected in the observation note. Students will not be allowed to enter into the lab without getting the previous experiment corrected in the record. In the record, LHS should be used for diagrams, tabular column, calculation and model graph (if any) and RHS should be used for writing aim, formula, apparatus required, procedure and the result. Diagrams, tabular column and graph should be drawn with pencil and procedure in blue ink and students should paste the graph along with the corresponding experiments neatly. Titles and subtitles should be in capital letters and it should be underlined only with black pen or pencil. Students who are late for the practical class will not be allowed to do their experiment. 100% attendance is compulsory for all the laboratory classes. Absentees will not be allowed to do their experiments in their subsequent classes. A place and number will be allotted to each student. Students have to follow this number for regular practical classes for the whole semester. Students should maintain silence while doing the experiment and any doubts should be clarified only with the staff members. There will be a plastic tray on each working table. All glass ware (except burette) will be kept in the tray. Do not place any glass apparatus on the working table. They should be kept only in the plastic tray. Do not keep the glass ware at the edge or corner of the table so that breakage of glass ware can be avoided. Always keep your place neat, clean and dry. There will be a white colour plastic bottle available in the tray. It should be used to fill distilled water and not the tap water. Distilled water will be kept at a particular place in the chemistry lab. Make sure for the distilled water before filling it in the bottle. Engineering Chemistry lab manual (SCY4051) 1 Regulations 2015

3 All glass wares should be washed first with tap water and then should be rinsed with distilled water. Numbered solution bottles are kept on the side tables in the lab. Students should take the bottles according to their seat number (for some solutions need not follow the seat number, consult with staff for more information). After the completion of experiment, these bottles should be replaced in the same place. The reagents for the experiments will also be on the side tables. Students should not bring them to their place as these reagents are common for all the students. Each concordant reading should be attested by the staff members before proceeding to the next part of the experiment. Without getting the readings attested, students should not proceed with the experiment. Students should wash all the glass ware after completing the experiment and should be replaced in the plastic tray. The instruments kept in the lab are already calibrated. These instruments should not be disturbed or tampered. All the instruments and electrodes should be handled carefully. Any breakage or damage to glass ware or equipment should be informed to the staff members (do not touch or clean the broken glass wares) immediately. Students should sign in the breakage register and the breakage amount will be collected. Materials like filter paper, glass beads etc. should not be thrown in the sink after their usage. Students are requested not to leave the lab without the permission of the staff in-charge. Your place will be checked by the assistants for cleanliness and for the replacement of the glass ware. Students have to leave the lab only after the period gets over. Concentrated acids, particularly sulphuric acid, should be added very carefully. More care has to be taken while adding any acid or while heating the glass wares. If any injury arises due to acid or heat, wash the area immediately with sufficient water and seek the medical assistance. How to fill a burette? Wash the burette and funnel with tap water. Check for any leakages. Inform the staff member, in case of leakage. Take small volume of distilled water, rinse the burette and funnel thoroughly. Keep the funnel in the burette and add small portion of the solution which should be taken in the burette. Rinse the burette and funnel thoroughly with that solution. Drain this solution in the sink and then fill the burette till the zero level. Open the stopper at the base and release the air bubbles from the bottom of the burette. Add more of the solution to adjust for the zero level till the lower meniscus coincides with the zero mark for colourless solutions (if the lower meniscus is not visible, as in the case of coloured solutions, upper meniscus can be used for zero adjustment). Now Engineering Chemistry lab manual (SCY4051) 2 Regulations 2015

the burette solution is ready for titration. The burette should be filled up to zero level every time before starting a new titration. How to use the pipette?

Take the pipette out by closing it with the index finger (finger should be dry) and rinse the pipette thoroughly by inverting the pipette. Drain the distilled water completely.

Always insert the pipette well into the solution to prevent sucking of solution into the mouth.

conical flask. After draining the solution, touch the bottom of the conical flask for complete draining of the solution.

You will be provided with a small volume of a solution in a small bottle. This solution has to be transferred into the standard flask without spilling even a drop.

4 the burette solution is ready for titration. The burette should be filled up to zero level every time before starting a new titration. How to use the pipette? Wash the pipette with tap water and check for any breakage, particularly at the tip. Insert the pipette into the wash bottle containing distilled water to draw water for rinsing. Take the pipette out by closing it with the index finger (finger should be dry) and rinse the pipette thoroughly by inverting the pipette. Drain the distilled water completely. After cleaning with distilled water, the pipette should be rinsed with the respective solution the same way as before. Always insert the pipette well into the solution to prevent sucking of solution into the mouth. When the solution reach the safety bulb, close the top of the pipette with the index finger and adjust the solution level to the mark present near the bulb and then drain the solution into the conical flask. After draining the solution, touch the bottom of the conical flask for complete draining of the solution. The last drop of the solution present in the pipette after complete draining of the solution should not be blown out. Now the solution is ready for titration. How to make up a solution? You will be provided with a small volume of a solution in a small bottle. This solution has to be transferred into the standard flask without spilling even a drop. Follow the instructions given below: Check for any breakage and wash the glass rod, funnel, volumetric standard flask and stopper thoroughly with tap water and rinse with distilled water. Keep the funnel on the volumetric standard flask. Carefully transfer the solution given in the small bottle into the volumetric standard flask through a glass rod and the funnel. While transferring, the solution bottle should touch the glass rod and the glass rod should be well inside the funnel. This is followed to avoid the spillage of the solution. After transferring the solution, use small volume of distilled water for rinsing the solution bottle and transfer the rinsing to the volumetric standard flask. The glass rod should not be taken away from the funnel. Again rinse the bottle with little distilled water and transfer the rinsing into the volumetric standard flask through the glass rod and the funnel. Repeat this procedure for 3 or 4 times. After ensuring the complete transfer of the solution, wash the glass rod with distilled water. Wash the funnel with distilled water. (Every time a small quantity of distilled water has to be added so that after all this process the total liquid volume in the standard flask will be less than the mark) Now add distilled water slowly up to the mark using a pipette. The lower meniscus should coincide with the mark (if the lower meniscus is not visible then upper meniscus can be considered). Close the stopper tightly and invert the standard flask and gently shake the solution by turning the standard flask up and down several times to get a solution of uniform concentration. Burette Funnel Standard flask Pipette Conical flask Glass rod Wash bottle Engineering Chemistry lab manual (SCY4051) 3 Regulations 2015

5 LIST OF EXPERIMENTS S. No. Name of the Experiment Page No. 1 Determination of Total Hardness of Water Sample by EDTA method 5 2 Estimation of Mixture of Acids by Conductometric Titration 9 3 Estimation of Fe 2+ by Potentiometric Titration 14 4 Determination of Molecular Weight of a Polymer by Viscosity Measurement Method 19 5 Determination of pka Value of Glycine Using ph Meter 24 6 Estimation of Iron by Using Photocolorimeter 29 Engineering Chemistry lab manual (SCY4051) 4 Regulations 2015

6 Expt. No. 1 Date 1. DETERMINATION OF TOTAL HARDNESS OF WATER SAMPLE BY EDTA METHOD AIM: To estimate the total hardness of the given sample of water by EDTA method. PRINCIPLE: Hardness of water is due to the presence of dissolved salts of calcium and magnesium. Hardness of water is determined by titrating a known volume of water sample with EDTA, using Eriochrome Black T (EBT) as the indicator, in the presence of ammonium hydroxide ammonium chloride buffer to maintain the ph at 10. APPARATUS & REAGENTS: EBT indicator. Burette, pipette, conical flask, EDTA, Standard hard water, NH4OH-NH4Cl buffer solution, PROCEDURE: TITRATION I - STANDARDIZATION OF EDTA SOLUTION: Pipette out 20 ml of the standard hard water into a clean conical flask. Add about 5ml of (NH 4Cl + NH4OH) buffer solution and a small quantity of Eriochrome Black T indicator. The solution turns to wine red in colour. Titrate against EDTA solution taken in the burette until the solution turns to steel blue colour. Repeat the titration for concordant values. Let V1 be the volume of EDTA consumed by standard hard water. TITRATION II - ESTIMATION OF TOTAL HARDNESS OF GIVEN WATER SAMPLE: Pipette out 20 ml of sample hard water into a clean conical flask. Add about 5 ml of (NH4Cl + NH4OH) buffer solution and a small quantity of Eriochrome Black T indicator. The solution turns to wine red in colour. Titrate against EDTA solution taken in the burette until the solution turns to steel blue colour. Repeat the titration for concordant values. Let V2 be the volume of EDTA consumed by the sample hard water. RESULT: Total hardness of the given sample of water = ppm (parts of CaCO 3 per million parts of water). Engineering Chemistry lab manual (SCY4051) 5 Regulations 2015

7 OBSERVATIONS AND CALCULATION: Titration I - Standardization of EDTA solution: Burette Pipette solution Indicator End point : EDTA solution : 20 ml of std. hard water + 5ml buffer solution : Eriochrome Black T : Wine red to steel blue Sl. No. Volume of Std. hard water Burette Reading Initial Final Volume of EDTA Concordant Value 1 ml of standard hard water = 1 mg of CaCO3 equivalent hardness..(1) 20 ml of standard hard water = 20 mg of CaCO3 equivalent hardness..(2) 20 ml of standard hard water consumes = V1 ml of EDTA..(3) From equation (1) and (2): V1 ml of EDTA = 20 mg of CaCO3 equivalent hardness 20 1 ml of EDTA = mg of CaCO3 equivalent hardness V 1 Titration II - Estimation of Total Hardness of Water: Burette Pipette solution Indicator End point : Standardised EDTA solution : 20ml water sample + 5ml buffer solution : Eriochrome Black T : Wine red to steel blue S. No. Volume of Given Water Sample Burette Reading Initial Final Volume of EDTA Concordant Value 20 ml of sample hard water consumes = V2 ml of EDTA 20 ml of sample hard water = V2 x 1 ml of EDTA 20 ml of sample hard water 20 = V2 mg of CaCO3 equivalent hardness V ml of sample hard water = V2 V 20 mg of CaCO3 equivalent hardness 1 V Total hardness of given water sample = V 1 ppm. Engineering Chemistry lab manual (SCY4051) 6 Regulations 2015

8 SHORT PROCEDURE DETERMINATION OF TOTAL HARDNESS OF WATER SAMPLE BY EDTA METHOD Titration I - Standardization of EDTA solution: Burette Pipette solution Indicator End point 1 ml of EDTA = 20 V1 : EDTA solution : 20 ml of std. hard water + 5ml buffer solution : Eriochrome Black T : Wine red to steel blue mg of CaCO3 equivalent hardness Titration II - Estimation of Total Hardness of Water: Burette Pipette solution Indicator End point : Standardised EDTA solution : 20ml water sample + 5ml buffer solution : Eriochrome Black T : Wine red to steel blue V Total hardness of given water sample = V 1 ppm. Result: Total hardness of the given sample of water = ppm (parts of CaCO 3 per million parts of water). Engineering Chemistry lab manual (SCY4051) 7 Regulations 2015

9 VIVA-VOCE QUESTIONS: 1. Define hard water and soft water. 2. Define hardness of water. 3. What are the hardness causing constituents? 4. Distinguish between carbonate hardness and non-carbonate hardness. 5. How is hardness of water expressed? (or) Bring out the significance of calcium carbonate equivalents? 6. Bring out the relationship between ppm and mg/lit. 7. How does eriochorme black-t function as an indicator in EDTA titration? 8. In EDTA titration NH4Cl-NH4OH buffer is used. Why? 9. Every soft water is not demineralized water whereas every demineralized water is soft water. Justify 10. Differentiate between soft water and demineralized water. 11. Name any two of the important disadvantages of using hard water for domestic purposes. Engineering Chemistry lab manual (SCY4051) 8 Regulations 2015

10 Expt. No. 2 Date 2. ESTIMATION OF MIXTURE OF ACIDS BY CONDUCTOMETRIC TITRATION AIM: To estimate the amount of acids present in the whole of the given solution. You are provided with standard 0.2 N sodium hydroxide solution. PRINCIPLE: During the titration of mixture of acids (strong acid HCl and weak acid CH3COOH) vs strong base (NaOH), initially the conductance is very high due to the presence of fast moving H + ions of strong acid. Upon titration, the fast moving H + ions are replaced by slow moving Na + ions. Therefore the conductance of the solution decreases. During the titration of NaOH vs HCl the following reaction takes place in the vessel. Na + OH + H + Cl Na + Cl + H2O After the end point there will be slow rise in the conductance of the solution due to the slight dissociation of weak acetic acid. As sodium hydroxide is added, the hydroxide reacts with the acid to form water and acetate. Na + OH + H + CH3COO Na + CH3COO + H2O A plot between volume of NaOH added versus the conductance of the solution, will give two intersection points. The first point corresponds to the first titre value between strong acid vs strong base. The second point corresponds to the second titre value between weak acid vs strong base. APPARATUS & REAGENTS: etc. Conductivity meter, beaker, burette, pipette, glass rod, sodium hydroxide, hydrochloric acid PROCEDURE: Makeup the given acid solution into a clean 100 ml standard flask with distilled water. Pipette out 20 ml of the made up acid solution into a clean 100 ml beaker. Pipette out 20ml of distilled water into the beaker. Rinse the conductivity cell thoroughly with distilled water and immerse into the beaker. Stir the solution gently and carefully with a glass rod. Measure the initial conductance of acid solution. Now add 1 ml of NaOH from the burette. Stir the solution carefully with the glass rod and note the conductance. Engineering Chemistry lab manual (SCY4051) 9 Regulations 2015

11 Continue the titration by adding NaOH (in an aliquot of 1 ml) from the burette. When we add NaOH the conductance initially decreases up to certain volume of NaOH. After that, the conductance starts increasing slightly for the addition of NaOH. After a particular volume the conductance increases rapidly. Plot a graph between the conductance values and volume of NaOH added as shown in the model graph. The first point of intersection of the two lines in the graph gives the first end point of the titration. Consider this value as V1. Consider the second point of intersection of the two lines in the graph as V3. V3 V1 gives the second end point of the titration. RESULT: The amount of hydrochloric acid present in the whole of the given solution = g. The amount of acetic acid present in the whole of the given solution = g. OBSERVATION S. No. Volume of NaOH added (ml) Conductance (m Mho) Engineering Chemistry lab manual (SCY4051) 10 Regulations 2015

12 CALCULATIONS Estimation of HCl: Volume of NaOH (V1) = ml (obtained from graph) Normality of NaOH (N1) = 0.2 N Volume of Mixture of acids (V2) = 20 ml Normality of strong acid-hcl (N2) = Equivalent weight of HCl = 36.5 (obtained V1 Amount of HCl present in 1000ml(x) = N from graph) The amount of HCl present in the whole of the given solution = Estimation of CH3COOH: x g Volume of NaOH (V4) = (V3-V1) ml (obtained from graph) Normality of NaOH (N1) = 0.2 N Volume of mixture of acids (V2) = 20 ml Normality of weak acid-ch3cooh (N3) = V4(obtained Equivalent weight of acetic acid = 60 from graph) Amount of acetic acid present in 1000ml (y) = N3 60 Model graph: The amount of acetic acid present in the whole of the given solution = y g Engineering Chemistry lab manual (SCY4051) 11 Regulations 2015

13 SHORT PROCEDURE ESTIMATION OF MIXTURE OF ACIDS BY CONDUCTOMETRIC TITRATION Aim: To estimate the amount of hydrochloric acid and acetic acid present in the whole of the given using 0.2N standard sodium hydroxide (NaOH). Principle: Initially the conductance is high due to the presence of fast moving H + ions. Upon titration the fast moving H + ions are replaced by slow moving Na + ions. Therefore, the conductance decreases on addition of NaOH solution. After the first equivalence point, the conductance increases slightly and rapidly after the second equivalence point. H + Cl + Na + OH Na + Cl + H2O Na + OH + H + CH3COO Na + CH3COO + H2O Procedure: Calibrate the conductivity meter with 0.1N KCl solution. Conductance = 13.6milli mhos Titrate Standard NaOH against HCl solution Burette Solution : Standard NaOH Pipette Solution : 20ml of made up acid solution + 20ml of distilled water End point : Obtained from graph Model Table: Model Graph: Volume of NaOH (ml) Conductance (mmhos) V 0.2 Normality of acid = 20 Equivalent weight of HCl = 36.5, Equivalent weight of CH3COOH = 60 Result: The amount of HCl present in the whole of the given solution Normality of HCl x 36.5 x 100 = = g The amount of CH3COOH present in the whole of the given solution Normality of CH3COOH = = g Engineering Chemistry lab manual (SCY4051) 12 Regulations 2015

14 VIVA-VOCE QUESTIONS: 1. What is conductance? 2. What are the different types of conductors? 3. Define Ohm s law. 4. What is the advantage of conductometric titration? 5. Why the conductance is decreasing initially? 6. What is the difference between specific conductance and equivalent conductance? 7. What is cell constant? 8. How will you calibrate a conductivity meter? 9. What is the unit of conductance? 10. What is the relation between conductance and temperature? 11. What is the relation between conductance and concentration of the solution? 12. What are the differences between anode and cathode? 13. What is ionic mobility? Engineering Chemistry lab manual (SCY4051) 13 Regulations 2015

15 Expt. No. 3 Date AIM: 3. ESTIMATION OF Fe 2+ BY POTENTIOMETRIC TITRATION To estimate the amount of ferrous ions present in the whole of the given solution. You are provided with s standard 0.1 N potassium dichromate solution. PRINCIPLE: The electrode potential of any redox system can be obtained by coupling it with a reference electrode (like saturated calomel electrode) of known potential (0.2422V). By connecting a cell with the calomel electrode, the potential of ferrous-ferric redox system can be determined. The redox cell can be represented as for which by applying the Nernst equation, Hg/Hg2Cl2, KCl(saturated)// Fe 3+ Ecell = ER.H.S _ EL.H.S - Fe 2+ / Pt E cell E o Fe / Fe Fe log n Fe Where E is the emf of the electrode, E o Fe 3 2 is the standard electrode potential for ferrous-ferric / Fe system, n is the number of electrons involved in the reaction, F is the Faraday s constant, R is the gas constant and T is the temperature. Ferrous ions are oxidized to ferric ions by adding potassium dichromate which simultaneously increases the e.m.f of the cell. A sharp increase in the e.m.f. at the end point which is due to complete conversion of ferrous to ferric ions. APPARATUS & REAGENTS: Potentiometer, standard calomel electrode, platinum electrode (indicator electrode), beaker, burette, pipette, glass rod, standard flask, potassium dichromate, ferrous solution and sulphuric acid. PROCEDURE TITRATION: Transfer the given ferrous ion solution into a clean 100 ml standard flask. Make up the solution with distilled water. Pipette out 20 ml of the made up solution into a 100 ml beaker and add 20 ml of dil. H2SO4. Immerse the platinum and calomel electrodes in the solution and connect them to the potentiometer. Stir the solution and note the initial constant e.m.f. of the solution. Then add 0.5 Engineering Chemistry lab manual (SCY4051) 14 Regulations 2015

16 ml aliquots of K2Cr2O7 solution from the burette and note the e.m.f. Initially, the difference in e.m.f. will be small followed by a large difference in the e.m.f. values near the end point. After the end point again the difference in e.m.f values will be small. By calculating E, V and E / V, a graph is plotted by taking volume of K2Cr2O7 solution (V) on the X-axis and E / V on the Y-axis. From the graph, the volume of K2Cr2O7 solution consumed is determined. RESULT: Amount of Fe 2+ ions present in the whole of the given solution = g. TITRATION: S. No. Volume of K2Cr2O7, V (ml) Observed e.m.f, E (milli volts) E V E / V (millivolts/ml) Engineering Chemistry lab manual (SCY4051) 15 Regulations 2015

17 CALCULATION: Volume of K2Cr2O7 solution (V1) = ml Strength of K2Cr2O7 solution (N1) = 0.1 N Volume of Fe 2+ solution (V2) = 20 ml Strength of Fe 2+ solution (N2) = V1 ( Obtained from graph) Amount of Fe 2+ ions present in 1000 ml (Y) = Normality of Fe 2+ Equivalent weight of Fe 2+ Amount of Fe 2+ ions present in 100 ml of the solution = = N Y 10 = g Model graph Engineering Chemistry lab manual (SCY4051) 16 Regulations 2015

18 VIVA-VOCE QUESTIONS: 1. What is a redox reaction? 2. Define oxidizing and reducing agents. Give egs. 3. Define e.m.f, standard electrode potential E o. 4. What is a reference electrode? Give examples. 5. What is an indicator electrode? Give examples. 6. Construct a calomel electrode and give its types. 7. Give the cell representation for redox reaction. 8. Write the Nernst equation for the ferrous-ferric system. 9. What happens to the e.m.f. of the cell when the [Fe 3+ ] ion concentration increases? 10. What are the advantages of potentiometric titration? 11. What will be the colour change of the working solution after the end point? 12. Why Platinum electrode is used as an anode? 13. Write the redox reaction for the experiment. 14. How the e.m.f. of the cell vary at the end point? 15. Represent a first derivative graph for the redox titration. Engineering Chemistry lab manual (SCY4051) 17 Regulations 2015

19 SHORT PROCEDURE ESTIMATION OF Fe 2+ BY POTENTIOMETRIC TITRATION Aim: To determine the amount of ferrous ions present in the whole of the given solution using 0.1N standard potassium dichromate (K2Cr2O7). Principle: For a ferrous ferric system the electrode potential is determined by combining with saturated calomel electrode to form a cell represented as Hg / Hg2Cl2, KCl (Sat) // Fe 3+, Fe 2+ /Pt Procedure: Titration : Standard dichromate Vs Ferrous ion Solution Burette Solution : Standard K2Cr2O7 Pipette Solution : 20ml of made up ferrous solution + 20ml dil. H2SO4 End Point : Obtained from the graph Equivalent weight of Fe 2+ = Model Table: Volume of Sl. K2Cr2O7, No V (ml) Observed emf, E (milli volts) E (mv) V (ml) E / V (mv/ml) Model Graph: ΔE/ΔV Strength of Fe 2+ solution (N2) = Amount of Fe 2+ ions present in 1000 ml of the solution (Y) Amount of Fe 2+ ions present in 100 ml of the solution = Volume of K 2Cr 2O 7 V1 ( Obtained from graph) = Normality of Fe 2+ solution Equivalent weight = N Y 10 = g Result: Amount of Fe 2+ present in the whole of the given solution = g. Engineering Chemistry lab manual (SCY4051) 18 Regulations 2015

20 Expt. No. 4 Date AIM: 4. DETERMINATION OF MOLECULAR WEIGHT OF A POLYMER BY VISCOSITY MEASUREMENTS To determine the molecular weight of the given polymer by viscosity method using Ostwald viscometer. PRINCIPLE: The viscosity of a polymer solution is high compared to that of the pure solvent. The molecular weight of a polymer is proportional to the intrinsic viscosity of its solution (η i) when the polymer molecular chain is extended to its full contour length. The value of intrinsic viscosity is proportional to the square root of the molecular weight M, when the polymer is in a solvent. The relationship between intrinsic viscosity and molecular weight is given by Mark-Kuhn-Hownik s empirical equation as, i KM where α is a measure of the shape of the polymer molecular chain (coiled or extended form) and the value is usually from 0.5 to 0.8. The value of the constant K depends on the polymer and the solvent involved. For a liquid flowing through a capillary tube, the time required to pass through the capillary tube is related to the absolute viscosity according to the equation: Pr 4 t 8Vl where V is the volume of the liquid which pass through the capillary, r is the radius of the capillary, l is the length of the capillary and P is the pressure head under which the liquid flow takes place. If η and ηo are the absolute viscosities of the polymer solution and the pure solvent respectively and t and t0 are their corresponding flow times and if the same capillary tube is used then, the relative viscosity is: t t o o Hence for each concentration calculate the values of η/η0 and ηsp (specific viscosity) sp t 1 to Engineering Chemistry lab manual (SCY4051) 19 Regulations 2015

21 From the plot of ηsp/c vs concentration of the polymer, intrinsic viscosity can be calculated. APPARATUS & REAGENTS: Viscometer (Ubblehodeor Ostwald), stop watch, beaker (50 ml, 100 ml), standard f lasks( 100ml, 25ml), pipette 10 ml and burette 50 ml. PROCEDURE: 2.5 g of the given polymer is exactly weighed and transferred into a 100 ml beaker. It is dissolved with minimum amount of solvent (water or benzene) with constant stirring using a glass rod. The polymer solution is transferred into a 100 ml standard flask and made upto the mark using distilled water. It is shaken for uniform concentration. The resulting solution is 2.5% polymer solution. 25 ml of 0.25%, 0.5%, 0.75%, 1%, and 1.25% polymer solutions are prepared as follows. Pipette out 2.5, 5, 7.5, 10, and 12.5 ml of 2.5% polymer solution in a 25 ml standard flask. Then make up the polymer solution with distilled water and shake the solution thoroughly. Pipette out 10 ml of each solution into a viscometer. The flow time of the solvent (t 0) and the polymer solution (t) in seconds is noted. The flow time can be determined as follows. Wash the viscometer and 10 ml pipette with distilled water and dry it. Fix the viscometer vertically in a stand. Pipette out 10 ml of the solvent into the lower bulb of the viscometer and suck the liquid carefully into the upper bulb, so that the liquid level is above the mark. Allow the liquid to flow freely. When the liquid level crosses the upper mark, start a stopwatch. When the liquid level crosses the lower mark, stop the stopwatch. Repeat it for two times. The average value is the flow time of water. Similarly determine the flow time of given polymer solutions at different concentrations. Tabulate the results. From the flow time we can calculate the specific viscosity. sp o 1 sp t t o 1 From the plot of ηsp/c versus concentration, the intrinsic viscosity (Y - intercept) ηi can be determined. Using ηi, α and K values, the molecular weight of the polymer can be determined. RESULT: The molecular weight of the given polymer sample = Engineering Chemistry lab manual (SCY4051) 20 Regulations 2015

22 Flow time of pure solent, t0 = sec. Sl. Conc. of the polymer No. solution, C % % % 4. 1% % Time of flow (sec) η/ η0 = t/t0 ηsp = (t/t0) - 1 ηsp/c ηi = KM α log ηi = log K + α logm log M = log ηi - log k α log M = X M = antilog of X Polymer solution α K Polyvinyl pyrolidone Water system x 10-5 dl/g Polyvinyl alcohol Water system x 10-5 dl/g MODEL GRAPH: Engineering Chemistry lab manual (SCY4051) 21 Regulations 2015

23 VIVA-VOCE QUESTIONS: 1. Define Viscosity. 2. What is Viscosity Coefficient of a liquid? 3. Define density of a liquid. 4. What is Specific gravity? 5. How is Specific gravity and density related? 6. What is the S.I unit of Viscosity Coefficient? 7. What are the factors that influence the viscosity of a liquid? 8. How does the viscosity vary with temperature? 9. Why should the viscometer to be dried before the measurements are done? 10. Why is acetone used for cleaning viscometer? 11. Why is viscometer not rinsed with given liquid or water? 12. Why do you require laboratory temperature for viscosity determination? 13. How is the viscosity of a liquid related to its mobility? 14. What is fluidity of a liquid? 15. What is effect of molecular weight on viscosity? 16. Explain another method used for determination of viscosity of liquid? Engineering Chemistry lab manual (SCY4051) 22 Regulations 2015

24 SHORT PROCEDURE DETERMINATION OF MOLECULAR WEIGHT OF A POLYMER BY VISCOSITY METHOD Aim: To determine the molecular weight of a polymer by viscosity method. Principle: The molecular weight of a polymer is proportional to the intrinsic viscosity of its solution (ηi). The relationship between intrinsic viscosity and molecular weight is given by ηi = KM α. Where α is a measure of the shape of polymer molecular chain. The value K depends on the polymer and the solvent used. Procedure: 2.5% of a polymer solution is prepared by dissolving 2.5gm of the polymer in 100ml of the solvent. From this 2.5% solution, 0.25%, 0.5%, 0.75%, 1% and 1.25% solutions are prepared. 10ml of this solution is pipetted out into a viscometer and the flow time is noted. The flow time for the solvent(t0) and all these solutions (t) are noted. The specific viscosity is given by: ηsp = (t/t0) 1 ηsp/c is plotted against C. The Y intercept is intrinsic viscosity (η i). Using α and K values the molecular weight is calculated using the formula: Model Graph: ηi = KM α SYSTEM K(dl/gm) α Poly vinyl alcohol - water 45.3x Model Table: Sl. Concentration of No. the polymer solution 1 Distilled water % 3 0.5% % 5 1.0% % Time of flow η/η0 = t/t0 ηsp = (t/t0) 1 ηsp / C Result: The molecular weight of the given polymer sample = Engineering Chemistry lab manual (SCY4051) 23 Regulations 2015

25 Expt. No. 5 Date 5. DETERMINATION OF pka VALUES OF GLYCINE BY ph TITRATION METHOD AIM: To determine the pka value of the given amino acid, glycine using ph titration method PRINCIPLE: Amino acids have the general formula NH2-CHR-COOH. They can act as both acids and bases. In water, most amino acids exist as zwitter ions, i.e., a dipolar ion. Thus, they are amphoteric molecules that can be titrated with both acid and alkali. Glycine, the simplest amino acid, has one acid and one amine group and is diprotic in nature. Isoelectric point, pi, is the ph of an amino acid at which the net charge on the molecule is zero. When such an amino acid is titrated against a base, it acts as an acid, and with an acid, it acts as a base. The ph of such a weak acid or base can be calculated from the Henderson-Hasselbalch equation ph [ basic species] pka log [ acidic species] APPARATUS AND REAGENTS: 0.1 N glycine, 0.1 N HNO3, 0.5 N NaOH, ph meter, ph glass electrode, burettes, beaker and buffer solutions (4, 7 and 9) for calibrating ph meter. PROCEDURE: 10 ml of the given 0.1 N amino acid, glycine is pipetted out into a clean 100 ml beaker followed by the addition of 10 ml of 0.1 HNO3 and 20 ml of distilled water. A ph glass electrode is rinsed in deionized water and immersed in the glycine solution. The ph of the mixture is recorded using a calibrated ph meter is in the range of A clean burette is taken and filled with 0.4 N NaOH. Add increments of 0.5mL of NaOH from the burette. The solution is stirred well using a glass rod and the change in ph is recorded. Initially, the ph of the solution increases steadily and then drastically at the isoelectric point and then increases steadily. The alkali is added in increments till the ph reaches to The readings are recorded in a tabular column as shown in Table 1. Engineering Chemistry lab manual (SCY4051) 24 Regulations 2015

26 The titration curve is plotted with Volume of NaOH on the x axis and ph on the y axis. The two plateaus on the curve obtained is noted which represents the pka values of glycine. These values are then compared with that reported in literature. RESULT: The two pka values of glycine are and. Engineering Chemistry lab manual (SCY4051) 25 Regulations 2015

27 Sl. Volume of No. NaOH Observed ph TITRATION CURVE OF GLYCINE Engineering Chemistry lab manual (SCY4051) 26 Regulations 2015

28 VIVA-VOCE QUESTIONS: 1. Define pka. 2. What is dissociation constant? 3. What are monoprotic and polyprotic compounds? 4. Give examples of monoprotic and diprotic acids. 5. Glycine is an example of monoprotic or polyprotic. Justify. 6. Define pi or Isoelectric point. 7. How can the pi of a polyprotic compound be calculated? 8. What happens when water is added to glycine? 9. How does an aqueous solution of glycine exist? 10. What happens when an acid is added to a zwitter ion of glycine? 11. What happens when a base is added to a zwitter ion of glycine? 12. What is zwitter ion or dipolar ion? 13. How many pka values does glycine have and what are they? 14. How do you prepare 0.1M solution of glycine, HCl and NaOH? 15. What are the titrants used to determine the pka values of glycine? 16. How is pka value determined from graph? 17. How are ph and pka value related? 18. Define Molarity and Normality. 19. How do you prepare 0.1N solution of glycine, HCl and NaOH? 20. How does the protonated form of zwitter ion of glycine exist? 21. How does the deprotonated form of zwitter ion of glycine exist? 22. Explain the migration of glycine at acidic and alkaline ph towards electrodes in an electric field. 23. Give the expression of Henderson-Hassellbalch equation. Engineering Chemistry lab manual (SCY4051) 27 Regulations 2015

29 SHORT PROCEDURE DETERMINATION OF pka VALUES OF GLYCINE BY ph TITRATION METHOD Aim: To determine pka value of the given amino acid, glycine using ph titration method Principle: Amino acids have the general formula NH2-CHR-COOH. They can act as both acids and bases. In water (neutral ph), most amino acids exist as zwitter ions, i.e., a dipolar ion. When an amino acid is titrated against a base, it acts as an acid, and with an acid, it acts as a base. The ph of such a weak acid or base can be calculated from the Henderson-Hasselbalch equation ph [ basic species] pka log [ acidic species] Procedure: Glycine vs. NaOH Burette solution: 0.1N HCl Pipette solution: 10 ml of 0.1 N glycine +10 ml of 0.1N HNO3+ 20 ml distilled water pka value obtained from the graph. Model Table: Glycine Vs NaOH Sl. Volume of No. NaOH Observed ph Model Graph: Result: The two pka values of glycine are and. Engineering Chemistry lab manual (SCY4051) 28 Regulations 2015

30 Expt. No. 6 Date AIM ESTIMATION OF IRON BY PHOTOCOLORIMETRIC METHOD To estimate the amount of Fe 3+ ion present in the given water sample using spectrophotometer. PRINCIPLE When a monochromatic light passes through a homogeneous coloured solution, a portion of incident light is reflected, a portion is absorbed and the remaining is transmitted. Where I0 = Ir + Ia + It I0 = Intensity of light incident on the solution Ir = Intensity of incident light reflected Ia = Intensity of incident light absorbed It = Intensity of incident light transmitted Ir is usually eliminated and hence I0 = Ia + It. The mathematical statement of Beer- Lambert s Law is given by T = I/I0 = 10 kcl Where T = transmittance of solution I = intensity of light leaving the solution I0 = intensity of light incident on the solution K = molar absorption coefficient C = concentration of the solution in moles/ litre l = length of absorbing layer (OR) A = log I0/I = k c l where A is the absorbance or optical density of solution i.e when a ray of monochromatic light passes through an absorbing medium, its absorbance decreases exponentially as the concentration of absorbing substance and the width or thickness increases independently. Keeping the path length constant (say l = 1 cm), the variation is only due to concentration, c. Fe 3+ ion alone does not give any colour in water solution. However, it develops a red colour when it reacts with potassium thiocyanate solution. Engineering Chemistry lab manual (SCY4051) 29 Regulations 2015

31 Fe KSCN [Fe(SCN)6] K + Red colour complex Further, this colour is in the blue region, (λ=480 nm). Spectrophotometer has a wide range of adaptability that allows selection of monochromatic light of any wavelength in the visible spectrum. INSTRUMENTATION The light source is an ordinary light bulb and monochromatic light is obtained by using either a glass prism or a diffraction grating. The monochromatic light then passes through the filter and is directed through a cell containing the sample. The incident light passes through the solution and hits the photoelectric cell and the output of this can be seen in the display. APPARATUS AND REAGENTS Photocolorimeter, 100 ml standard flasks, 10% potassium thiocyanate, 1:1 hydrochloric acid solution, standard ferric ion solution (100 ppm). PROCEDURE Prepare a series of standard solution containing 2-10 ppm of iron by adding 1 ml of 1:1 H Cl and 1 ml of 10% potassium thiocyanate solution. The red solution is made up to 100 ml in a standard flask. Switch on the photocolorimeter and warm it up for about 10 minutes. Adjust the monochromator at the wavelength λ = 480 nm.the blank is distilled water with the reagents used for the experiment. Keep the blank solution in the cuvette and adjust the instrument to transmittance corresponding to 100 or absorbance is zero. Similarly, place the various standard concentrations of iron solutions in the cuvette one by one and measure the corresponding absorbance. Also, measure the absorbance of the unknown solution. Draw the calibration graph between the absorbance of the standard solution and concentration. The concentration of the unknown solution is determined from the calibration graph. RESULT: Amount of iron present in the given solution = ppm. Engineering Chemistry lab manual (SCY4051) 30 Regulations 2015

32 λ = 480 nm Distilled water Blank = zero absorbance. Sl. No. Concentration Absorbance 1 Blank 0 2 2ppm 3 4ppm 4 6ppm 5 8ppm 6 10ppm 7 Unknown Spectrophotometer Model graph Engineering Chemistry lab manual (SCY4051) 31 Regulations 2015

33 Viva-voce questions 1. What is meant by ppm? 2. State Beer-Lambert's law. 3. What is absorbance? 4. What is colorimeter? 5. Mention the significance of colorimeter? 6. What is the principle of colorimeter? 7. What is the reaction condition for estimation of iron? 8. Write the chemical reaction for the experiment. 9. What is the colour of the ferric-thiocyanate during complex formation? 10. What is the diagrammatic representation of principle of photocolorimeter? 11. What are the steps to operate the photocolorimeter? 12. What is the blank solution of the estimation of iron by photocolrimeter? 13. What is meant by unknown solution? Engineering Chemistry lab manual (SCY4051) 32 Regulations 2015

34 SHORT PROCEDURE ESTIMATION OF IRON BY USING PHOTOCOLORIMETRIC METHOD Aim: To estimate the amount of Fe 3+ ions present in the whole of the given solution using photocolorimetric method. Principle: According to Beer-Lambert s law, when a monochromatic light is passed through a transparent homogeneous solution, the intensity of transmitted light decreases exponentially with the concentration and thickness of the solution. Where, It = intensity of transmitted light Io = intensity of incident light e = base of neutral logarithm k = a constant C = concentration l = thickness of the solution It/Io = e -kcl Fe 3+ ion alone does not give any colour in water solution. However, it develops a red colour when it reacts with potassium thiocyanate solution in acid medium. Procedure: Fe KSCN [Fe(SCN)6] K + Red colour complex Standard iron solutions 2 ppm, 4 ppm, 6 ppm, 8 ppm and 10 ppm Standard iron solution + 1 ml of 1:1 HCl + 1 ml of potassium thiocyanate made upto 100 ml. Model Table: λ= 480 nm. Distilled water Blank = zero absorbance S.No Concentration Absorbance 1 2 ppm 2 4 ppm 3 6 ppm 4 8 ppm 5 10 ppm 6 Unknown Result: Amount of iron present in the given solution = ppm. Engineering Chemistry lab manual (SCY4051) 33 Regulations 2015

Dharmapuri LAB MANUAL. Regulation : 2013 Branch. : B.E. All Branches GE6163-CHEMISTRY LABORATORY - I E NG

Dharmapuri LAB MANUAL. Regulation : 2013 Branch. : B.E. All Branches GE6163-CHEMISTRY LABORATORY - I E NG Dharmapuri 636 703 LAB MANUAL Regulation : 2013 Branch Year & Semester : B.E. All Branches : I Year / I Semester GE6163-CHEMISTRY LABORATORY - I E NG ANNA UNIVERSITY: CHENNAI SYLLABUS R 2013 GE6163 - CHEMISTRY