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LABORATORY MANUAL CHE102ENGINEERING CHEMISTRY LABORATORY

LMCHE 102: ENGINEERING CHEMISTRY LABORATORY

Some rules to be followed in the Lab: General Rules: 1. Entry without lab coat in chemistry lab is strictly prohibited. 2. Mobile phones should be switched off and kept in the bag during lab hours. 3. No group discussions are allowed in the lab. 4. Clean the apparatus as well slab after your experiment is finished. 5. Do not do any indiscipline activity in lab as you are under strict cc-TV surveillance. 6. Always bring the lab manuals with you. 7. Do not use laptop while performing the experiments. 8. Switch off electrical apparatus after their use. 9. Do not throw filter papers in sink dispose all solid waste in dustbin. 10. Liquid waste must be deposited in the waste containers designated for Chlorinated organic solvents, Organic solvents and aqueous waste. Precautionary Rules: 1. Never pipette out strong acids and bases with your mouth, it can be dangerous, therefore use measuring cylinders for such chemicals. 2. Never try to smell the chemicals as it can be dangerous for you. 3. Cap the bottles after taking chemical because uncovered bottles can be a source of harmful fumes. 4. In case of any accidental spill over of any chemical on you, report your teacher or lab technician immediately. 5. Report your lab technician if any breakage of glass apparatus takes place.

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LMCHE 102: ENGINEERING CHEMISTRY LABORATORY

Table of Contents S.No 1 Title of Experiment To determine the hardness of the given hard water sample by EDTA method. You are provided with Standard Hard Water (1 ml of SHW =1 mg of CaCO3). 2 To determine the rate constant of hydrolysis of ethyl acetate 8-11 catalyzed by HCl. To determine the strength of given solution of ferrous ammonium sulphate by titrating it against potassium dichromate solution. 4 To estimate the nickel content in the given sample using dimethyl 15-17 glyoxime. To Separate the mixture of amino acids by thin layer 18-22 12-14 Page No. 4-7

3

5

chromatography. 6 7 8 To Identify the elements present in given organic compound. To determine the dissociation constant of acetic acid using pH-meter. To determine the Strength of hydrochloric acid solution by titrating it against sodium hydroxide solution conductometrically 9 To test the validity of Beer-Lamberts law and also determine 37-42 unknown concentration of solution using colorimeter 23-26 27-31 32-36

Appendix Common Apparatus/Instruments used in Chemistry lab 43-45

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LMCHE 102: ENGINEERING CHEMISTRY LABORATORY

Experiment No. 1 1. Experiment: To determine the hardness of the given hard water sample by EDTA method. You are provided with Standard Hard Water (1 ml of SHW =1 mg of CaCO3). Equipment required: Burette, Burette stand, Titration flask, Pipette, Beakers, Funnel etc. Materials required: Standard Hard water, Sample hard water, EDTA solution, Eriochrome black-T (EBT), Buffer Solution. 2. Learning Objectives: I) The purpose of this experiment is to determine the hardness of water by measuring the concentrations of calcium in water samples by titration. II) To gain knowledge about complexometric titration. III) To know the purpose of EDTA used IV) To know about use of buffer solution: The buffer being used has composition NH4Cl and NH4OH. Its pH is the order of 10.5. V) To know the purpose of indicator THEORY Complexometric titrations are mainly used to determine the concentration of divalent cations such as calcium, magnesium, zinc, copper, lead etc. Hard water is the water that has high concentration of calcium and magnesium ions. The Ethylenediaminetetraacetic acid (EDTA) is the most commonly used complexant. EDTA is a chelating agent. It is able to form coordination complex with metal ions present in hard water. Although these reactions are easy to perform, it is necessary to maintain well defined pH. How does the indicator work? The indicator used here is organic molecule capable of forming a colored complex with the metal cations to be determined. The indicator-metal ion complex would be less stable than the complex formed by the cation with the corresponding titrant (EDTA). The indicator used is Eriochrome black T. (i) When indicator is added to hard water it combines with free metal ions present in water giving metal indicator complex which is wine red in colour. HIn2- + M2+ MIn- + (Wine red)Page 4

H+

(M=Ca2+, Mg2+)

LMCHE 102: ENGINEERING CHEMISTRY LABORATORY

(ii) When EDTA solution is added to the titration flask it combines with the free metal ions giving metal EDTA complex, which is stable and colourless. H2Y2+ M2+ MY2+ 2H+

(Colourless) (iii) When all the free metal ions are exhausted, next drop of EDTA removes the metal ion engaged with indicator and the original blue colour of indicator is restored. H2Y2+ MIn MY2+ HIn2- + H+ (Blue) 3. Outline of Procedure: A. Standardization of EDTA solution: a) Fill the burette with EDTA solution. b) Pipette out 10 ml of standard hard water in the titration flask. Add to it 2-3 ml of buffer solution and two drops of Eriochrome Black-T indicator. A wine red color appears. c) Titrate this solution against EDTA solution taken in a burette till wine red color changes to blue. d) This is the end point. Recovered the volume of EDTA consumed as A ml. Repeat the procedure to get at least three concordant readings. Table1: Standardization of EDTA S. No. Burette readings Initial (R1) 1. 2. 3. 4. 5. Final (R2) Volume of EDTA Consumed (R2 - R1) mL

B. Determination of Total Hardness: a) Pipette out 10 ml of sample hard water in the titration flask. Add to it 2-3 ml of buffer solution and two drops of Eriochrome Black-T indicator. A wine red colour appears.Page 5

LMCHE 102: ENGINEERING CHEMISTRY LABORATORY

b) Titrate this solution against EDTA solution taken in a burette till wine red colour changes to blue. c) This is the end point. Recovered the volume of EDTA consumed as B ml. Repeat the procedure to get at least three concordant readings. Table 2: Determination of Total Hardness S. No. Burette readings Initial (R1) 1. 2. 3. 4. 5. Calculations: (a) Standardisation of EDTA solution: 1 ml of standard hard water = 1 mg of CaCO3 10 ml of S.H.W. A ml of EDTA 1 ml of EDTA = 10 mg of CaCO3 = 10 mg of CaCO3 = 10/A mg of CaCO3 = A ml of EDTA Final (R2) Volume of EDTA Consumed (R2 - R1) mL

(b) Calculation of total hardness: 10 ml of sample hard water Now 1 ml of EDTA B ml of EDTA 10 ml of sample hard water 1 ml of hard water sample = B ml of EDTA = 10/A mg of CaCO3 = B 10/A mg of CaCO3 = B x 10/A mg of CaCO3. = B x 10/A x 1/10 mg of CaCO3.

1000 ml of hard water sample = B x 10/A x 1/10 x 1000 mg of CaCO3. Hence total hardness = 1000 x B/A ppm

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LMCHE 102: ENGINEERING CHEMISTRY LABORATORY

4. Required Results: Parameters: Volumetric analysis. Relationships: determine how much EDTA is consumed for 1 mL of Standard Hard Water, which is then, can be used for the calculation of unknown hardness. Graphs: NA Error Analysis: Ask for the actual hardness and calculate the % error.

% Results: The hardness of given sample hard water is =.......... ppm. % error =%. Scope of result The determination of water hardness is a useful test to measure the quality of water for households and industrial uses. Hard water can cause serious problems in industrial setting, where hard water is monitored to avoid costly breakdown in boilers, cooling towers and other equipments that handles water. 5. Cautions: i. The burette, pipette and conical flask should be washed properly and then rinsed with distilled water. ii. iii. Redistilled water should be employed for preparing the EDTA solution. The colour change near the end point is very slow and thus should be observed very carefully. 6. Learning outcomes: to be written by the students in 50-70 words.

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LMCHE 102: ENGINEERING CHEMISTRY LABORATORY

Experiment No. 2 1. Experiment: To determine the rate constant of hydrolysis of ethyl acetate catalyzed by HCl. Equipments requirements: Six conical flasks, burette, pipette, Stop watch, Water bath etc. Materials required: 0.1N NaOH, ethyl acetate, 0.5 N HCl, Phenolphthalein. 2. Learning Objectives: I) II) III) IV) To make the concepts of chemical kinetics understandable. To know how to determine the rate constant of a reaction. To gain knowledge about chemical kinetics of pseudounimolecular reactions. Student will learn how to find the order of reaction with the help of rate constant at different time intervals. V) VI) VII) To prove that order of reaction is an experimental concept. To know the effect of temperature on rate of reaction. To gain knowledge about acid base titration.

THEORY This reaction is an example of psuedounimolecular reactions. Since water is present in large excess, its concentration is practically constant throughout the reaction. The reaction is catalysed by H+ ions of an acid (HCl). The concentration of HCl (catalyst) also remains constant. Therefore, the rate of reaction depends upon only on the concentration of ester. Rate = -dx/dt = k [CH3COOC2H5 ]. Hence reaction is of first order. During the hydrolysis of ester, acetic acid is produced. Therefore, the progress of reaction is followed by determining the amount of acetic acid formed at different time intervals.H

CH3COOC2H5 + H2O

CH3COOH + C2H5OH

A definite quantity of the reaction mixture is withdrawn after different time intervals and is titrated against a standard solution of alkali. The amount of alkali used is equivalent to the total amount of HCl present initially and the amount of acetic acid formed. The volume of alkali used at the start of reaction is equivalent to amount of HCl alone. Hence, the amount ofPage 8

LMCHE 102: ENGINEERING CHEMISTRY LABORATORY