chemistry Honours(H3) 1st sem 2013 previous year BSc question paper | Assam University

TDC Odd Semester Examination, 2013

CHEMISTRY

(Honours)

( 1st Semester)

Course No. : CHMH—103

(Physical Chemistry—I)

Full Marks: 35

Pass Marks: 12

Time: 2 hours

The figures in the margin indicate frill marks for the questions

Answer five questions, taking one from each Unit

UNIT—I

1. (a) What is the significance of van der Waals’ constants a and b?
(b) Deduce the Critical constants of a gas in terms of van der Waals’ constants. 4

(c) Write Berthelot and Dieterici’s equation explaining the terms involved in the equation. 1+1=2

2. (a) How can you calculate second virial coefficient using van der Waals’ equation? 2
(b) A gas obeying van der Waals’ equation has a critical temperature 31 °C and critical density O341 g/cc. If the molecular weight of the gas be 44, find van der Waals’ constants a and b. 3
(c) Obtain the following equation from van der Waals’ equation:
(PV/RT)=1+bP/RT-a/RTV+ab/RTV

UNIT—II

3. (a) Derive the Bragg equation for X-ray crystallography. 3
(b) Draw and explain the structure of graphite. 2
(c) Identify thc following crystal system and give one example of the solid.
a≠b≠c; a=b=c=90

4. (a) (i) Describe Lane’s method used for analysing the structure of crystal.
(ii) Discuss Born-Haber cycle with suitable example. 2+2=4
(b) A certain solid X (atomic mass 27) crystallizes in an f.c.c. structure. If the density ofXis 27g/cnl3, what is the length of the edge? 3

UNIT—III

5. (a) What is meant by—
(i) Joule-Thomson coefficient;
(ii) inversion temperature? 1+1=2
(b) What do you mean by state function and path function of a thermodynamic system? Give examples.
(c) Show that the inversion temperature is given by T = 2a/Rb

6. (a) Deduce the relationship
μ=-1/C(ბH/ბP)
(b) A gas expands against a variable external pressure given by P = V atmosphere, where V is the volume of the gas at each stage of expansion. Further in expanding from 10 to 100 L the gas undergoes a change in internal energy du = 100 calories. How much heat has been absorbed?
(c) Classify the following into extensive and intensive properties
(i) Enthalpy
(ii) Viscosity
(iii) Surface tension
(iv) Heat capacity

UNIT—IV

7. (a) Derive the phase rule equation thermodynamically.
(b) Draw and discuss the phase diagram of Mg-Zn.

8. (a) Explain why the fusion curve of ice has a negative slope whereas the sublimation curve has a positive slope in the phase diagram of water.
(1) (i) Describe the phase diagram of lead silver system.

(ii) From Pb-Ag diagram, illustrate the principle of Pattinson process of desilverization of lead. 3+2=5

UNIT—V

9. (a) The rate constant of a first-order 2.303 a reaction is k1 = log , where a is the initial concentration of the reactant and x is the concentration of the product after a time t. Write the above equation in slope-intercept form of a straight line and draw a curve between log (a — x) and t. Write the slope and intercept from the curve. 1±1+1=3
(b) Derive the Euler reciprocity relation. What is an exact differential?

10. (a) How many words can be formed with the letters of the word ‘SILCHAR’? How many of these will begin with ‘S’?
(b) In how many ways can a college cricket eleven be chosen out of 14 players? How many of them will always include a particular player as captain? 1 /2+ 11/2=3
(c) Distinguish between an exhaustive and a null event.

14J—500/72 N—13/ODD/CHMH—103/248