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Physical Chemistry-Chemistry-BSC-Nagpur-Winter-2018

Bachelor of Science (B.Sc.) Semester—2 Examination
CHEMISTRY (Physics Chemistry)

Optional Paper—1
Time : 3 Hours
Maximum Marks : 50

N.B. :— (1) All questions are compulsory and carry equal marks.
(2) Draw well labelled diagram wherever necessary.

1. (A) What is Carnot Cycle ? Derive an expression for efficiency of a reversible carnot engine working
between temperature T1 and T2. [5M]

(B) Derive Van’t Hoff ’s equation upto its integrated form. [5M]


(C) Show that Delta Suni. > 0 in an irreversible process. [2½M]

(D) Calculate the Free energy change when 4 moles of an ideal gas expand from a pressure of 10 atm. to
1 atm. at 298 K. (R=8.314 JK¯1 mol¯1 ) [2½M]

(E) For the reaction, N2(g) + 3H2(g) = 2NH3(g), the free energy changes at 298 K and 308 K are
–16.65 kJ and –14.10 kJ. Calculate the heat of reaction at 308 K. [2½M]

(F) Derive the relation, Kp = Kc × (RT)Dn. [2½M]

2. (A) State Phase rule. Draw and discuss the salient features of phase diagram of water system. [5M]

(B) What is critical solution temperature ? Discuss the system :

(a) with lower critical solution temperature, and

(b) with upper critical solution temperature. [5M]


(C) Explain :—

(i) Phase, and

(ii) Components.[2½M]

(D) Discuss Pattinson’s Process of desilverization of lead. [2½M]

(E) State and explain the Raoult’s law of ideal solution. v

(F) In the distribution of benzoic acid between water and benzene, the following results were obtained :
C1 (in water) 1.50 1.95 2.97
C2 (in benzene) 24.20 41.2 97.0
Assuming that benzoic acid exists as single molecule in water, show that it exists as double molecules in
benzene. [2½M]

3. (A) Define :—

(i) Mass defect, and

(ii) Binding energy
Calculate the binding energy per nucleon of 16O,
8 whose mass defect is 0.1370148 amu.
(1 amu = 931.5 MeV) [5M]

(B) What is dipole moment ? How is it used to calculate percentage ionic character of a polar covalent
bond ? The bond length of H-I bond is 1.60 Å and its dipole moment is 0.38 D. Calculate the percentage
ionic character of H-I bond. (ID = 3.336 ×10¯30Cm) [5M]


(C) Compare nuclear shell model with liquid drop model. [2½M]

(D) Give the application of radioisotopes in medical science and agriculture. [2½M]

(E) Explain polarisation of molecules in the electric field. [2½M]

(F) How ortho, meta and para substituted isomers of benzene can be distinguished from dipole moment
measurements ? [2½M]

4. (A) Derive the equation of rate constant for first order reactions. A first order reaction is 20% completed in
10 minutes. Calculate the rate constant of the reaction. [5M]

(B) Discuss transition state theory. Derive an expression for the rate constant based on equilibrium constant.  [5M]


(C) Define rate of reaction. Write various factors affecting on the rate of reaction. [2½M]

(D) Describe half-life period method for the determination of order of reaction. [2½M]

(E) Calculate the activation energy for the decomposition of N2O5 whose rate constants at 300 K and
340 K are 2.2×10–5 S–1 and 5.5×10–3 S–1 respectively. (R = 8.314 JK–1 mol–1)   [2½M]

(F) Discuss the Lindemann’s theory as applied to the unimolecular reaction. [2½M]

5. Attempt any TEN questions out of the following :—

(i) Give any two statements of second law of themodynamics.

(ii) Define standard free energy change.

(iii) State law of chemical equilibrium.

(iv) Write reduced phase rule equation.

(v) What are azeotropes ?

(vi) State Nernst’s Distribution law.

(vii) Define nuclear fusion.

(viii) What is polar covalent bond ?

(ix) Why CO2 has zero depole moment ?

(x) Define molecularity of reaction.

(xi) What is pseudo unimolecular reaction ?

(xii) Write Arrhenius equation.        [10M]

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