B.Sc. (General) 4th Semester
Chemistry
Same for B.Sc. Microbial & Food Technology)
Paper-XV: Physical Chemistry-B
Time Allowed: Three Hours]
Maximum Marks: 22
Note: (1) Attempt five questions in all, selecting at least one question from each Section. Section E is compulsory. (2) Use of log tables and simple calculators is allowed.
SECTION-A
1. (a) State and explain 'Nernst Distributions Law'. Prove that the law does not undergo modification if the solute undergoes chemical combination with one of the solvents except that the numerical value of partition coeffiecient changes.
(b) What do you understand by 'Critical Solution Temperature' (CST) ? Explain a system which has both upper CST as well as lower CST.
2 (a) Define 'Gibb's Phase Rule'. Derive it thermodynamically.
(b) What do you understand by congruent and incongruent melting points? What is the number of components and the degree of freedom at congruent melting point of a system, consisting of two components?
SECTION-B
3. (a) Define 'Transport Number'. Describe briefly the principle underlying the determination of transport number by 'Hittorf's Method'.
(b) Calculate the concentration of hydronium ions in an aqueous solution of acetic acid in which 0.05 moles of acetic acid are dissolved in 250 ml of solution. Given that ka value for acetic acid is 1.8x10-5.
4. (a) Explain two interionic effects :
(i) Relaxation Effect
(ii) Electrophoretic Effect.
(b) The transport numbers of Ag+ ion and NO3, ion in an aqueous solution of AgNO3, are 0.466 and 0.534 respectively. The molar conductance at infinite dilution for this solution is 116.5 Scm2 gm eq-1 Calculate:
(i) ionic conductances of Ag and NO3- ions
(ii) Absolute velocity of the two ions.
SECTION-C
(a) Derive 'Nernst equation' for the following general reversible cell reaction.
aA + bB ScC + dD
(b) Standard Electrode Potential of Copper Electrode at 298 K is +0.34 V, calculate the concentration limit beyond which the electrode will have a negative potential.
(b) Write down the 'Debye Huckel Onsagar' equation for strong electrolytes.
(c) Will the molar conductance at infinite dilution of a decinormal aqueous solution of a dibasic acid be the same as its equivalent conductance at infinite dilution or different?
(d) What do you understand by the temperature coefficient of emf of a galvanic cell.
(e) How can the feasibility of a cell reaction be predicted from its cell potential.
(f) Give two conditions which are necessary for the validity of 'Distribution Law.
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