Master of Science II (Physical Chemistry)Examination: Oct/Nov
2016 Semester IV (New CGPA)
SLR No. Day
Date Time Subject Name Paper
No. Seat No.
SLR SD
249
Tuesday
22/11/2016
02.30 PM
To
05.00 PM
Molecular Structure-II
C
XV
Instructions: Attempt five questions.
Section-I (question is compulsory.
Attempt any two questions from Section II and any two questions
from Section III
Answers to all 5 questions (from Section II, III) should be
written in the one and the same answer book.
All questions carry equal marks.
Figures to the right indicate full marks.
Use of log table and calculators in allowed.
Total Marks:70
SECTION I
Q.1 Compulsory: 14
Draw polarizibility of a molecule.
According to Debye equation the orientation polarization is proportional to square
of the dipole moment. True or false.
The value of magnetic permeability for vacuum is
Write the expression for magnetic susceptibility according to Curie law.
The cylindrical charge cloud around acetylenic triple bond causes shielding effect
in NMR. True of false.
13C is NMR active while 12C is not. Why?
An ESR spectrum of an electron gives four lines. Predict the number equivalent
protons with which the electron is interacting with.
What is the value of g-factor for free electron?
What is Doppler Broadening in Mossbauer spectroscopy?
Mention the main factor on which chemical shift in Mossbauer spectroscopy
depends.
What is Curie point in Mossbauer spectroscopy?
According to Debye equation write the expression for the induced polarization.
Which of the molecules BF3, PCI3, and NH3 are polar?
What do you mean by Larmor frequency?
SECTION II
Q.2 Describe the vapour-temperature method of determining dipole moment of a
molecule.
07
Derive Curie-Weiss law and explain how Curie point can be determined. 07
Page 1 of 2
Q.3 Explain the Bhatnagar-Mathur method of determining magnetic susceptibility. 07
Explain with the help of chemical shift concept in NMR why OH proton
requires low field and CH proton requires high field for methanol.
07
Q.4 Explain with suitable example the calculation of number of equivalent protons
from NMR spectra.
07
Using Langevin theory of paramagnetism derive an expression for molar
susceptibility.
07
SECTION III
Q.5 Derive conditions for resonance of an unpaired electron for its ESR spectrum. 05
What is isomer shift in Mossbauer spectroscopy? Explain with examples. 05
The ESR spectrum of methyl radical occurs at 330 mT in a spectrometer
operating at 9250 MHz. Calculate the value of g.
9.2732 x 10-24 h 6.626 x 10-34 Js)
04
Q.6 Describe the working of a Mossbauer spectrometer with a neat sketch. 05
Explain the nature of ESR spectrum obtained for benzene anion. 05
Calculate the recoil velocity of 119Sn Mossbauer nucleus if the emitted γ-ray
has the frequency 5.76 x 1018 Hz(N 6.023x1023, h 6.626 x 10-34 Js, c 3.0
x 108ms-1, Mass of 119Sn 119 x 10-3 kg 6.023 x 1023 19.767 x 10-26 kg)
04
Q.7 Write a note on any three of the following: 14
Refraction method of dipole moment determination.
Limitations of Langevin's theory
Spin- spin relaxation.
13C NMR Spectroscopy