Master of Science II (Physical Chemistry)
Examination: Oct/Nov 2016 Semester III (New CBCS)
SLR No. Day
Date Time Subject Name Paper
No. Seat No.
SLR
SD-243
Monday
21/11/2016
02:30 P.M
to
05:00 P.M
Molecular Structure- I
C
XI
Instructions: Answer any five questions.
All questions carry equal marks.
(Section-I) Q.1 is compulsory.
Attempt any two questions from Section II
Attempt any two questions from Section III
Draw neat and labeled diagrams wherever necessary.
Use of log table and calculators in allowed.
Total Marks:70
SECTION I
Q.1 Answer the following: 14
Define a symmetry operation.
Which is the principle axis of rotation in BCl3 molecule?
What is the point group of ammonia molecule?
For a rigid rotator what is the value in terms of B of a transaction J=1 to
Give an example of a prolate symmetric top molecule.
Write the expression for the distortion constant D of a non-rigid rotator in terms
of B.
Among CH3OH and CH3OD which of them has the higher frequency for the O-H
stretching vibration?
Define zero point energy of a harmonic oscillator.
In IR spectroscopy if the transition occurs with selection rule then such
transition is called as
The term symbol for a state 2D3/2. Find S and L.
The continuum observed below the true dissociation energy of a molecule is
called
What are stokes lines?
Why homonuclear diatomic molecules give pure rotational Raman spectra while
they do not give pure rotational spectra?
If a molecule of formula XY2 has two IR and One Raman active bands in its
spectra then the molecule possess a
SECTION II
Q.2 Identify various symmetry elements for a planar MX4 molecule and discuss the
relationship between the different axes of rotation
07
Write down the character table for of a C2v group and discuss their classification
into various reducible representations.
07
Page 1 of 2
Q.3 Derive expression for the rotational energy of a rigid diatomic molecule and
draw the diagram for the allowed rotational energies.
07
Derive expression for the Jmaxfor a rigid diatomic rotator. If the rotational
constant of CO in 3.8626 cm-1 calculate the value of Jmax at 300 K.
(Given h=6.626x10-34Js, k=1.381x10-23 c=3.0 x 108
07
Q.4 Obtain expression for fundamental, first and second overtone absorption
frequencies of a diatomic molecule considering it as an unharmonic oscillator.
07
The fundamental and first overtone of 14N16O are central at 1876.6 cm-1 and
3724.2 cm-1 respectively. Calculate the equilibrium vibrational frequency, the
unharmonicity constant, zero point energy and the force constant of the
molecule.
07
SECTION -II
Q.5 Describe in detail the instrumentation of a Raman spectrometer. 05
If the bond length in hydrogen molecule is 0.0747 nm what would be the
positions first three lines of its rotational Raman spectrum? What if the effect of
nuclear spin on the spectrum?
05
Illustrate hydrogen atom spectrum with electronic energy level diagram. 04
Q.6 Give an account of electronic spectrum of hydrogen molecule with various
transitions and specify selection rules.
05
Explain the terms progression and sequences and find the quantum numbers for
the states represented by 3P2, 3P1 and 3P0.
05
Discuss the factors which contribute for the width of spectral lines. 04
Q.7 Write a note on any three of the following: 14
Orthogonality theorem
Classification of molecules based on their moment of inertia
Mutual exclusion principle
Birje- Sponer extrapolation