Electronic Spectroscopy

Question 1

The electronic spectra in the visible range span is __________
a) 25000-72000 cm-1
b) 25000-50000 cm-1
c) 12500-25000 cm-1
d) 15000-30000 cm-1

Answer 1

c) 12500-25000 cm-1

Question 2

Which of the following transitions are of weak intensities and lie in the visible region?
a) n→n*
b) σ→σ*
c) π→π*
d) n→σ*

Answer 2

a) n→n*

Question 3

Arrange the various electronic transitions in the order of increasing energy.
a) n→σ* < π→π* < n→π* < σ→σ*
b) n→π* < π→π* < n→σ* < σ→σ*
c) n→σ* < n→π* < π→π* < σ→σ*
d) σ→σ* < π→π* < n→π* < n→σ*

Answer 3

b) n→π* < π→π* < n→σ* < σ→σ*

Question 4

What is the position of the band of alkanes?
a) 190 nm
b) 185 nm
c) 217 nm
d) 150 nm

Answer 4

d) 150 nm

Question 5

Which of the following organic compound shows transition due to conjugation?
a) Alkenes
b) Saturated aliphatic ketones
c) Conjugated dienes
d) Alkanes

Answer 5

c) Conjugated dienes

Question 6

Which of the following is not an auxochrome group?
a) –OH
b) –SH
c) –OR
d) –O2

Answer 6

d) –O2

Question 7

Which of the following shift leads to the decreased intensity of absorption?
a) Hypochromic
b) Hyperchromic
c) Hypsochromic
d) Bathochromic

Answer 7

a) Hypochromic

Question 8

Which of the following is an application of electronic spectroscopy?
a) Detection of impurities
b) Control of purification
c) Study of kinetics of the chemical reaction
d) All of the mentioned

Answer 8

d) All of the mentioned

Question 9

What will be the absorbance if %T = 80?
a) 0.5
b) 0.05
c) 0.097
d) 0.97

Answer 9

c) 0.097 ( A=log(1/T) or log(Io/I) )

Question 10

Which of the following is a limitation of the Lambert-Beer’s law?
a) Scattering of light due to particles
b) Fluorescence of sample
c) Non-monochromatic radiation
d) All of the mentioned

Answer 10

d) All of the mentioned