MES PONNANI COLLEGE
THIRD SEMESTER
SECOND INTERNAL EXAMINATION
CHEMISTRY CORE COURSE
PHYSICAL CHEMISTRY I
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Time : 2.5 hours
Marks : 30
Part A
Answer all questions. Each carries a weightage of ¼
Which among the following is an expression that gives the critical pressure, Pc?
a) a/27b2
b) 8a/27Rb
c) 3b
d) None of these
The vapour pressure of non-polar liquid is
a) fairly high as compared to polar liquids
b) fairly low as compared to polar liquids
c) the same as that of polar liquids
d) none of these
Heat absorbed or evolved at constant pressure in a process is equal to the change in
a) entropy
b) internal energy
c) enthalpy
d) bond energy
A reaction will never be spontaneous if
a) ∆H is positive and ∆S is negative
b) ∆H is negative and ∆S is positive
c) ∆H is negative and ∆S is negative
d) ∆H is positive and ∆S is positive
The number of possible microstates for a system of two vibrating molecules with a total
energy of 2hv is
a) 3
b) 2
c) 6
d) 4
Which among the following is the correct relation?
a) ∆G0 = RT ln K
b) ∆G0 = - RT ln K c) ∆G0 = RT / ln K d) ∆G0 = -2.303 RT ln K
Kp = Kc for a reversible reaction when ∆n = ________
A non-linear molecule with n atoms has ________ vibrational degrees of freedom.
Exothermic reactions involving a decrease in entropy become spontaneous if ∆H is ______
T∆S in magnitude.
In a process, heat absorbed or evolved at constant volume is equal to the change in ______
The observed molar refraction of an aliphatic conjugated polyene is found to be greater than
the calculated value. This phenomenon is called ________
A gas cannot be liquefied if its temperature is above its ________
Part B
Answer all questions. Each carries a weightage of 1
Explain the effect of temperature on the viscosity of a gas.
Define surface tension of a liquid. What is the unit of surface tension? How does it vary with
temperature?
Define inversion temperature. What relation does it have with Joule – Thomson coefficient?
Define efficiency of heat engine.
State the free energy criterion for an equilibrium state?
Obtain the relation between dA = -SdT - PdV
Write expressions for
a) translational partition function
b) rotational partition function
c) vibrational partition function
In how many ways can four A molecules and six B molecules be arranged in a row so that no
two A molecules are together.
How is Kc related to Kp?
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Part C
Answer 5 questions. Each carries a weightage of 2
Using van der Waals’ equation, calculate the pressure exerted by 1 mole of gas enclosed in a
1.5 dm3 flask at 400K. a = 3.0 atm dm6 mol-2; b = 0.05 dm3 mol-1.
Parachor is both an additive and consecutive property. Explain.
State and explain Carnot’s Theorem.
Derive an expression for the entropy of mixing in isothermal mixing of gases.
Derive Gibbs – Helmholtz relation.
With adequate explanation, derive Maxwell – Boltzmann distribution law.
State and explain law of mass action.
Part D
Answer 2 questions. Each carries a weightage of 4
a) Describe with theory the capillary rise method of determining -------- of a liquid.
b) What is optical exaltation? Explain.
a) Show that – (∆G)T,P = - wuseful
b) Derive an expression for the free energy change in a reversible isothermal process.
a) What is meant by thermodynamic probability? How does it differ from statistical
probability?
b) Show that S = k lnW