M.Sc. (Semester IV) (CBCS) Examination Mar/Apr-2018
Physical Chemistry
MOLECULAR STRUCTURE II
Time: 2½ Hours
Max. Marks: 70
Instructions: Attempt in all Five questions. Section I is compulsory. Attempt any two questions from section II any two questions from section III. All questions (Section II and III) should be written in one answer book. All questions carry equal marks. Figures to the right indicate full marks. Use of log table and calculator is allowed.
Section I
Q.1
Answers the following:
14
Define Dipole Moment.
Write the expression for molar polarization in terms of dielectric constant of the medium.
Which of the molecules H2O, CO2 and H2O2 are polar?
Write the relationship between volume and mass susceptibility.
What is the limitation of Gouy method of determining magnetic susceptibility?
When a nucleus has even number of protons and neutrons what would be its spin?
Write the equation for Larmor frequency in terms of magnetic moment and angular momentum of a spinning particle.
In an AX2 species what is the splitting pattern of resonance of nucleus
13C is NMR active while 12C is not. Why?
10) Which of the following show ESR spectrum, H2, CH3 and CO2?
11) The ESR transitions are observed in which region of electromagnetic spectrum?
12) Mossbauer spectroscopy involves nuclear transitions as a result of γ-ray absorption. True or False.
13) Name the standard absorber adopted for Mossbauer spectroscopy.
14) What is Doppler Broadening in Mossbauer spectroscopy?
Section II
Q.2
Derive Debye equation for molar polarization of a polar molecule.
07
Explain the Ebert's method of determining dipole moment.
07
Q.3
Derive an equation for intensity of total magnetization using Langevin theory of paramagnetism.
07
Calculate the molar susceptibility of pyridine by using Pascal constants (Given atomic susceptibilities per g atom of H and ring N are -6.0×10-6, -2.93×10-6 and -4.61×10-6 respectively)
07
Q.4
In NMR spectroscopy for a nucleus with obtain expression for allowed energy levels and frequency of transition in presence of magnetic field.
07
Explain with suitable example the calculation of number of equivalent protons from NMR spectra.
07
Page 2 of 2
SLR-UF-220
Section III
Q.5
Describe how the ESR spectrum helps to study kinetics of electron transfer reactions.
05
Explain the nature of ESR spectrum obtained for benzene anion.
05
Calculate the frequency for an unpaired electron in a magnetic field strength of 0.35 T g=2.0,β=9.2732×10−24 JT−1,h=6.626×10−34 Js
04
Q.6
Explain in detail the principle of Mossbauer spectroscopy.
05
Discuss the parameters required for evaluating Mossbauer Spectra.
05
The energy of emitted γ-rays from first excited state of 57Fe nucleus is 14.4 keV. Calculate its recoil energy (N=6.023×1023,1keV=1.6×10−19 J,c=3.0×108ms−1, Mass of 57Fe= 57 × 10-3 kg/6.023×1023=9.46×10−26kg)
04
Q.7
Write short notes on any Three.
14
Dipole moment and ionic character
Chemical Shift
Larmour frequency
Doppler broadening in Mossbauer spectroscopy