Conductance, Electrochemistry and Chemical Kinetics (DSC-16, Chemistry-06) — DU B. Sc. Life Science (Chemistry) Previous Year Question Papers

1. Answer any five. Each carries equal marks. (a) (b) (c) (d) (e) (f) (3×5) Equivalent conductance increases while conductivity decreases with dilution of solution of electrolyte. Explain. Transport number of Cl– ion in aqueous solution of HCl is 0.16 and it is 0.62 in aqueous solution of NaCl. Explain. Ionic Molar Conductivity at infinite dilution increases as Li+, Na+, K+, Rb+ Explain the terms specificity and selectivity in catalysis with examples. The first order reaction never achieves completion. Explain. If we double all the coefficients in a cell reaction, the charge number 'n' is doubled and the emf is unchanged. Explain. 2. (a) (b) (c) Draw and discuss the titration curves obtained during the conductometric titration of : (i) An aqueous solution of CH3COOH with aqueous solution of NaOH. (ii) An aqueous solution of HCl with aqueous solution of NH4OH. (5) A cell contains 0.10 mol dm–3 aqueous KCl, which at that concentration has a molar conductivity of 129 ohm–1cm2mol–1. The measured resistance was 28.44 ohm, When the same cell was filled with 0.05 mol dm–3 NaOH aqueous solution the resistance was 31.6 ohm. Find the molar conductivity of aqueous NaOH at that concentration. (5) Define Ionic Mobility. What is its unit? Write the relation between transference number and ionic mobility. (5) 3. (a) (b) (c) Derive the expression for the determination of the pH of the solution using glass electrode. Mention two advantages of glass electrode. (5) The emf of the cell Ag | AgCl (s) | KCl (soln) | Hg2Cl2(s) | Hg is 0.0455 V at 298 K and the temperature coefficient is 3.38 × 10–4 V K–1. The cell reaction is Calculate ΔG, ΔH and ΔS at 298K. (5) Explain the potentiometric titration curves Mohr salt and K2Cr2O7. Discuss the redox pairs involved in the reaction (i) Before equivalence point (ii) After equivalence point (5) 4. (a) What are the advantages of using salt bridge in electrochemical cells? KCl and NH4NO3 are frequently used to prepare salt bridge. Explain. (5) (b) Given that Write the cell representation of the following chemical reaction. Determine, whether the given reaction proceeds in forward or backward direction at (c) Write short notes on : (i) Daniel cell (ii) Electrochemical series (2.5×2) 5. (a) Write the integrated rate equation for a first-order reaction. For a reaction A → Products, the following data is given : (i) Determine the order of reaction. (ii) Calculate the rate constant. (5) (b) Derive the expression for its half-life of a second order reaction. A second-order reaction has a rate constant k=3.3×10–2 dm3 mol–1 s–1. If the initial concentration of the reactant is 0.05 mol dm–3 calculate its half-life. (5) 6. (a) Derive the expression for rate of a reaction involving specific acid catalysis. (5)