MCH-13 2025 SOLVED ASSIGNMENT

Description

ASSIGNMENT
MCH-013: General Physical Chemistry
Course Code: MCH-013
Assignment Code: MCH-013/TMA/2025
Maximum Marks: 100
Note: Attempt all questions. The marks for each question are indicated against it.
1.
2.
3.
4.
Answer any five of the following in brief.
a)
b)
c)
d)
e)
f)
g)
(a)
Give the physical significance of Helmholtz energy.
What is the effect of temperature on chemical potential?
Explain the molecular partition function in brief.
What is the improper rotation of the molecules? Explain with a suitable example.
Give the characteristics of the unimolecular reactions.
Define the primary and secondary salt effects on the rate of reactions in solution.
Why the conventional kinetic methods are not useful to study the fast reactions?
(2´5)
Determine the conditions for the spontaneity and equilibrium for following combinations of ΔH and
ΔS for a given process.
(i)
∆” <0 and ∆% > 0
(ii) ∆” > 0 and ∆% < 0 (iii) ∆" > 0 and ∆% > 0, and
(iv) ∆% = 0.
(b)
(i)
(5)
Two moles of an ideal gas expand isothermally at 300 K from 7 bar to 3 bar. Calculate the change
in the Helmholtz energy and Gibbs energy for the process.
(ii) Define partial molar volume and give its physical significance.
(a)
(b)
(a)
Give Stirling’s approximation and outline its significance. Calculate the % error introduced in
computing the value of 10! by using this approximation. (Given ln 2= 0.69 and ln 3= 1.01)
(i)
A system consist of two energy level (! and (” which are singly and triple degenerate,
respectively. Calculate the partition function of the system.
Or
Derive the relation between molecular and canonical partition function.
(ii) Derive an expression for the rotational partition function.
(i)
ii)
Define Tetrahedral and Octahedral voids in three dimensional close packing.
(3+2)
(5)
(2)
(2)
(3)
If atoms of element B form HCP lattice and 2/3rd of tetrahedral voids are occupied by those of
the element A,what is the formula of the compound formed by the elements A and B?
(iii) State the law of constancy of interfacial angles.
(2+2+1)
(b)
(i)
Show the following planes in cubic unit cells
i)
ii)
(110) in Primitive cubic cell
(111) in Face-centred cubic cell and
iii) (200) in Body-centred cubic cell.
(ii) Give the difference between screw Axis and glide Plane by using suitable illustrations.
or
Identify all the symmetry elements in trans C2H2Cl2or B2Cl6
(3+2)
5.
(a) Give the salient features ofthe collision theory and calculate the factor that relates the collision theory
with Arrhenius Equation.
(5)
(b) (i) Discuss the Lindemann-Christiansen mechanism for unimolecular reactions and give the
Hinshelwood’s modification of this mechanism.
(ii) What are two important features of the expression for rate of activation as per RRK theory? (3+2)
6.
7.
8.
9.
10.
Answer any five of the following in brief.
a) Give the principle of ultrasonic relaxation methods for the determination of the rates of the fast
reactions.
(2´5)
b) Explain the difference between homogeneous and heterogeneous catalysis with suitable examples.
c) Describethe lock and key hypothesis of the enzyme action.
d) What is the role of solvent in the Debye-Huckel model of a solution of an electrolyte?
e) Why did we need the modification in the Debye-Huckel theory?
f)
Give the mathematical expressions of any two type of Maxwell and Boltzmann distribution of
molecular speeds and name the terms involved.
g) What is the effect of pressure and temperature on thermal conductivity?
(a) Derive the expression of the rate constant for reactions in solution in terms of activity where the
reference standard state for the reactants is the gaseous state.
(b) (i) What is the difference between diffusion controlled and activation-controlled reactions.
(ii) Discuss the stopped flow method for the study of fast-reactions with suitable schematic
diagram and outline its advantages over continuous flow method.
(5)
(1+4)
(a) What is adsorption in homogeneous catalysis? Derive an expression for Langmuir monolayer
adsorption isotherms for adsorption at sufficiently low concentrations.
(b) (i) What is the difference between competitive and uncompetitive enzyme inhibition?
(ii) Derive the mathematical rate expression for competitive enzyme inhibition and give the
graphical representation of Lineweaver-Burk plot.
(a) (i) Write the basic assumptions of the Debye-Huckel theory.
(ii) Calculate the ionic strength of
i)
ii)
(b) (i)
0.08 mol kg-1 solutions of Ca(NO3)2 and
the solution consisting of 6.3 g of MgCl2, 5 g of AlCl3 and 500 g of water.
List different methods of experimental determination of activity coefficients.
(ii) Explain the principle for the experimental determination of activity and activity coefficient
from solubility measurements.
(a) (i) What are the limitations of phenomenological approach to transport properties?
(1+4)
(1+3+1)
(2)
(3)
(2)
(3)
(2)
(ii) Using the Fick’s first law of diffusion, derive the mathematical expression that provides the link
between the phenomenological and thermodynamic treatment of diffusion phenomenon.
(3)
(b) (i) Why is conductivity not a suitable quantity to compare the conduction behaviour of different
electrolytic solutions?
(2)
(ii) Define thermal conductivity. Why the thermal conductivity of gases is independent of pressure up
to a reasonably high pressure.