CH 151 Engineering Chemistry Laboratory

1 Laboratory MANUAL. Engineering Chemistry Laboratory . (For First Year Programmes). COURSE CODE: CY 151. (Images are used for the non-commercial academic purposes, non-profit). Name of the student: Roll No.: Department of Chemistry National Institute of Technology, Meghalaya CH 151 Engineering Chemistry Laboratory General instructions to the students I. Laboratory safety The following points are important and must be followed to avoid any kind of accidents inside the Laboratory : a) Do not smoke, drink and eat inside the Laboratory . b) Try to wear Laboratory coat and safety goggles. c) Do not perform any unauthorized experiments without the permission of the instructors.

2 D) For any kind of chemical burn, wash the area with plenty of water and inform your instructor promptly. e) Do not pipette out liquids by mouth use suction bulbs. f) Do not try to smell, taste any chemicals without the instructions of the concerned person. g) Do not add water to the concentrated acids. h) Do not touch any unknown chemicals by hands. i) Before leaving the Laboratory , wash your hands properly. II. General rules a) Try to understand the experiment before you start it. If you have any query, discuss with the instructor. b) If some reagent/apparatus is not found, ask your Laboratory attendant.

3 C) Finish the experiments within the specified time period. d) Regular submission of the Laboratory note book is mandatory. Late submission will not be entertained for evaluation. e) Never use mobile phones inside the Laboratory . III. Scientific aspects While you are in the process of writing Laboratory notebook, please keep the following points in mind: a) Scientific notations b) Proper units c) Number of significant digits d) Error analysis e) Graphs i. it must have a name and the axes should be specified ii. the data points should be clear on the graph iii. if possible, the error bars may be provided 2.

4 CH 151 Engineering Chemistry Laboratory List of experiments Sl. No. Title of the experiment Page No. 1 Estimation of Fe(II) in Mohr's salt solution using standard 5-8. KMnO4 solution via Redox titration. 2 Estimation of Fe(II) in a solution using standard K2Cr2O7 9-11. solution via potentiometric titration. 3 Precipitation titration of potassium chloride versus silver nitrate 12-14. ( potentiometric titration). 4 Conductometric titration of an unknown acid solution using a 15-17. standard base solution. 5 Conductometric determination of CMC of a surfactant (sodium 18-21. lauryl sulphate). 6 pH-metric titration of an unknown acid solution using a 22-24.

5 Standard base solution. 7 Complexometric determination of hardness of water. 25-28. 8 determination of polymer molecular weight via viscosity 29-32. measurements. 9 Kinetic study of ester hydrolysis catalyzed by acid and base. 33-36. 10 Spectrophotometry on copper sulphate solution. 37-39. 3. CH 151 Engineering Chemistry Laboratory Experiment No.: 1. Estimation of Fe(II) in Mohr's salt solution using standard KMnO4 solution via Redox titration. Theory: Titrations in which a reducing agent is titrated against an oxidizing agent or vice versa are called Redox titration. In a redox reaction if one substance is oxidized the other is reduced.

6 Oxidation is defined as the process in which loss of electron from the element takes place and reduction is a process where electrons are accepted by the element or the ion. The reagent which undergoes reduction is an oxidizing agent and the reagent which undergoes oxidation is a reducing agent. The oxidation and reduction are complementary to one another and takes place simultaneously. The equivalent weight of an oxidizing and reducing agent can be obtained by dividing molecular weight of the compound by the total number of electrons that are gained or lost in a reaction per molecule of the substance.

7 As the change in colour in acid base indicator depends on the pH of the reaction mixture, the change in colour of the indicator in redox titration depends upon the electrode potential of the system. Therefore, a redox indicator has to be chosen in such a way that its potential lies within that of the system. In this titration, KMnO4, the oxidizing agent is the self indicator as it is strongly coloured (purple) and decolorizes afterreduction. Potassium permanganate is purple in its oxidized form (MnO4 ) but its reduced form (Mn2+) is colorless in acidic medium. 4. CH 151 Engineering Chemistry Laboratory As, the titration proceeds, the MnO4 will converted to Mn2+ and simultaneously Fe2+ will converted to Fe3+.

8 When whole of the reducing agent (Fe2+) will consumed, the oxidizing agent (MnO4 ) cannot be reduced, then the addition even one drop of KMnO4 solution given its colour to the solution. This indicates the end point of the titration. Apparatus: Burette, pipette, conical flask, burette stand and clamp Chemicals: KMnO4, H2SO4, Mohr's salt [(NH4)2SO4, FeSO4, 6H2O]. Procedure: 1. Primary standard Mohr's salt solution was provided. 2. Secondary standard KMnO4 and unknown Fe(II) solution was provided. 3. Standardization of KMnO4 solution by standard Mohr's salt solution: Pipette out 20. mL of standard Mohr's salt solution into a 100 mL conical flask, add 20 mL of dilute H2SO4.

9 (1:8 V/V). Titrate with standard KMnO4 solution from the burette with constant stirring till the first permanent pink color develops in the solution. Repeat thrice. 4. Estimation of Fe (II) in the given solution: Pipette out 20 mL of unknown Fe(II) solution in a 100 mL conical flask, add 20 mL of dilute H2SO4 (1:8 V/V). Titrate with standard KMnO4 solution of known strength till the first permanent pink color develops throughout the whole mass of the solution. Take minimum 3 readings. 5. CH 151 Engineering Chemistry Laboratory 6. CH 151 Engineering Chemistry Laboratory 7. CH 151 Engineering Chemistry Laboratory Experiment No.

10 2: Estimation of Fe(II) in a solution using standard K2Cr2O7 solution via potentiometric titration Theory: This experiment involves the determination of the percentage of ferrous iron in an unknown samplemixture by redox titration with potassium dichromate solution as the standard using: (i) ferroin indicator (ii) potentiometric titration. The net ionic balanced equation for the titration is: Apparatus:Burette, pipette, conical flask, burette stand, clampand potentiometer/pH-meter with electrode. Chemicals: K2Cr2O7 (M/40) solution, 1 M H2SO4, Mohr's salt [(NH4)2SO4, FeSO4, 6H2O], phosphoric acid (85%), indicator solution.