Chem-DSE-6: Quantum Chemistry and Spectroscopy — DU B. Sc. Life Science (Chemistry) Previous Year Question Papers

3. (a) Write the mathematical expressions for the momentum operator Fx and potential energy operator V. (b) Give any four characteristics of a well-behaved wave function. (c) What is normalization of the wavefunction? Normalize the wavefunction V/n (x) = A sin ("X) for a particle in 1-D box of length I'. (d) Name and explain the theory which forms the basis for the electronic spectra of conjugated systems. What is the minimum excitation energy for linear molecule butadiene, given that the average C-C bond distance is 140 pm? (3,3,4,5) 4. (a) Define Lambert - Beer's Law. What are its limitations? (b) IR signal for stretching of C-C bond is at lower frequency than C-C bond. True or False. Give reasons. (c) Write short note on any two of the following: (li) Auxochromes and Chromophore (iii) Hypsochromic and hyperchromic shift (d) The 'H"CI molecule shows pure rotational lines at the following frequencies (cm 1) 20.7, 41.5, 62.0, 83.0, 103.8. Calculate the bond distance of HCI. (My =1.673 × 1027kg, 5. (a) Sketch fundamental vibrations of CO2 molecule. Which of them will be IR active? (b) How would isotopic substitution 160 by 1"O alter the microwave spectrum of CO? (c) How many translational, rotational and vibrational degree of freedom are there in HO and CHa molecules? (d) The fundamental vibration frequency of 'NO is observed at 1870 cm-!. Calculate the zero-point energy and force constant of the molecule. (3,3,4,5) 6. (a) Indicate with the help of the Jablonski diagram, the various processes by which the excited electronic states get deactivated. What is the difference between fluorescence and phosphorescence? (b) A molecule XY is studied by microwave spectroscopy under the rigid rotator approximation. Draw its schematic line spectrum. What is the structural information that can be obtained from this spectrum? (c) State the conditions for a molecule to be rotationally and vibrationally active. Which of the following molecules HCI, N2, CO, H¿O? Will give rise to observable rotational and vibrational spectra. (d) Calculate the transmittance, absorbance and the molar excitation coefficient of a solution which absorbs 90% of a certain wavelength of light when the beam passes through a 1 cm cell which contains a solution of molarity 0.25M. (3,3,4,5)