# Spectroscopy of Analysis MCQ with Answers for IIT JAM 2023

Practice Spectroscopy of Analysis MCQ with Answers for IIT JAM 2023

## Spectroscopy of Analysis MCQ with Answers for IIT JAM 2023

1. Hooke’s law relates the restoring force, F to the displacement q as

(a) F = -Kq
(b) F = Kq
(c) F = Kq2
(d) F = -Kq2

2. The intensity of an absorption band is always proportional to the

(a) Atomic population
(b) Molecular population of the initial state
(c) Molecular population of the final state
(d) Temperature

3. The vibrational stretching frequency of diatomic mo
molecule depends on

(a) Force constant
(b) Masses of two atoms
(c) Both a and b
(d) None

4. Force constant is expressed in

(a) Dynes cm-1
(b) dyne Å-1
(c) Nm-1
(d) All

5. q for NO, CO, HCI is 0.048 Å, 0.05 Å, 0.10 Å. Thus q is

(a) Larger when the force constant is smaller
(b) Smaller when the force constant is smaller
(c) Larger when the force constant is larger
(d) None

6. Since the nuclei in a polyatomic molecule do not always vibrate in a simple harmonic manner, there arises

(a) Harmonicity
(b) Anharmonicity in molecular vibrations
(c) Fundamental frequencies
(d) All

7. The frequency of vibration of H2 is 4159 cm-1 and dissociation energy is 4.5 eV. Assuming that it vibrates as a SHO, its vibrational quantum number corresponding to dissociation energy, D is

(a) 8
(b) 10
(c) 7
(d) 6

8. The vibrations, without a centre of symmetry are, active in

(a) Infrared but inactive in Raman
(b) Raman but inactive in IR
(c) Raman and IR
(d) None

9. The frequency of vibration of a bond is a function of

(a) Force constant of the bond
(b) Masses of the atoms involved in bonding
(c) Both a and b
(d) Bond order

10. The order of decreasing vibrational frequency for C-Cl, C-Br, C-C, C-O and C-H is

(a) C-H, C-C, C-O, C-CI, C-Br
(b) C-Cl, C-Br, C-C, C-H, C-O
(c) C-O, C-H, C-Br, C-Cl, C-C
(d) C – Br, C-CI, C-C, C-O, C-H

11. The increasing order of stretching frequencies for C ≡ C; C = C and C – C is

(a) C – C > C = C ≡ C
(b) C ≡ C > C = C > C – C
(c) C – C > C = C < C ≡ C
(d) C = C < C – C > C ≡ C

12. Ethanol and glycol in CCI4 exhibit broad O – H structure near 3350 cm-1 in IR spectra.On dilution with CC14 the spectrum of glycos does not change but that of ethanol exhibits a sharp band at 3600 cm-1 in addition to band at 3350 cm-1 because

(a) Intermolecular H-bonding is concentration dependent
(b) Intramolecular H-bonding is not affected on dilution
(c) Both a and b
(d) None

13. In the IR spectrum of aroyl chloride, a weak band near 1750 cm-1 results from

(a) inductive effect
(b) Fermi resonance between C = O band and first overtone
(c) conjugation effect
(d) All

14. Compound, C3H10 shows absorption at 1380 cm-1. It is

(a) Pentene
(b) Cyclopentane
(c) Pentyne
(d) All

15. Ketenes absorb in IR at a very high frequency (2150 cm-1) because

(a) The inner C is sp-hybridised
(b) The more s character in a bond, the stronger it is
(c) Inner C is sp2 hybridised
(d) Both a and b

16. Ring strain in lactone (cyclic ester) or a lactam (cyclic amide)

(a) Increases carbonyl stretching frequency
(b) Decreases carbonyl stretching frequency
(c) Increases C = C frequency
(d) Decreases C = C frequency

17. In α – haloketones

(a) Two C = O stretching bands are observed
(b) One band has normal frequency
(c) Other band is at higher frequency due to eclipsed interaction between halogen atom and C = O group
(d) All statements are correct

18.The wave number of IR absorption is ________ the reduced mass.

(a) directly proportional to
(b) inversely proportional to
(c) independent of
(d) directly proportional to square of

19. The number of vibrational degrees of freedom in C6H5CH5 will be

(a) 39
(b) 15
(c) 18
(d) 40

20. Which of the following molecules will not show infrared spectrum?

(a) H2
(b) HCI
(c) CH4
(d) H2O