CHEMISTRY (Physical 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) State and deduce the following from kinetic gas equation :

(i) Avogadro’s law and

(ii) Graham’s law of diffusion. [5M]

(B) Define :

(i) Critical volume

(ii) Critical temperature and

(iii) Critical Pressure.

The critical temperature and critical pressure of chlorine are 419 K and 93.1 atmosphere respectively.

Calculate the van der-Waal’s constants for chlorine gas. [5M]

**OR**

(C) Discuss Maxwell-Boltzmann’s distribution of molecular velocities. [2½M]

(D) Calculate the temperature at which RMS velocity of oxygen molecule will be equal to Hydrogen

molecule at 20 K. [2½M]

(E) Give the explanation of deviation of real gases by means of van der Waal’s equation of state. [2½M]

(F) Explain compressibility factor and Boyle temperature. [2½M]

2. (A) Derive Bragg’s equation for diffraction of X-rays. The first order diffraction from a certain crystal

is observed at an angle of 20.6° with X-rays of wavelength 22.91 nm. Calculate the interplanar

spacing. [5M]

(B) State and explain :

(i) Law of constancy of interfacial angles and

(ii) Law of rationality of indices. [5M]

**OR**

(C) What are Miller indices ? The Weiss indices of a certain plane are

3

1

,

2

1

and ¥. Find Miller

indices. [2½M]

(D) Draw (100), (110) and (111) planes of simple cubic crystal. [2½M]

(E) Discuss Laue’s method for determination of crystal structure. [2½M]

(F) Why Bragg’s method show that KCl is simple cubic though it is face centred cubic like

NaCl ? [2½M]

3. (A) What are intermolecular forces ? Discuss the following intermolecular forces in liquids :

(i) Dipole—induced dipole interactions and

(ii) London forces. [5M]

(B) How surface tension of a liquid is determined by capillary rise method ? At what height will a

liquid rise in a capillary tube having 0.1 mm diameter ?

(Density of liquid = 1.3 × 10^{3} kgm^{–3}

Surface tension of liquid = 6.5 × 10^{–3} Nm^{–1}

Acceleration due to gravity = 9.8 ms^{–1}). [5M]

**OR**

(C) What are liquid crystals ? Discuss cholesteric liquid crystals. [2½M]

(D) How relative viscosity of a liquid is determined by Ostwald’s viscometer ? [2½M]

(E) The molar refraction of acetic acid is 13.3 × 10 ^{–6} m^{3} mol^{–1} and its density is 1.046 × 10 ^{3} kgm^{–3}.

Calculate refractive index of acetic acid. [2½M]

(F) What is parachor ? Discuss application of parachor in structure determination. [2½M]

4. (A) Give the assumptions and derive an expression for Langmuir adsorption isotherm. [5M]

(B) Write BET equation. How is it used in the determination of surface area of the absorbent ? [5M]

**OR**

(C) What are the important applications of adsorption ? [2½M]

(D) Explain with examples homogeneous and heterogeneous catalysis. [2½M]

(E) Explain auto catalysis with examples. [2½M]

(F) Write a note on enzyme catalysis. [2½M]

5. Attempt any ten questions of the following :

(i) State any two postulates of Kinetic theory of gases.

(ii) Define mean free path.

(iii) Write van der Waal’s equation of state for n moles of real gas.

(iv) Define space lattice.

(v) Identify the crystal structure with the dimensions of unit cell :

a = b = c and a = b = g ¹ 90°

(vi) Draw unit cell of CsCl.

(vii) Why the liquid drop is spherical ?

(viii) What is intrinsic viscosity ?

(ix) Define refractive index.

(x) What are inhibitors ?

(xi) Define the term chemical adsorption.

(xii) Write Michaelis-Menten equation. [10M]

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