Questions and Discussion

1. Questions and Discussions

2. 1. UV-Vis. Spectroscopy of organic compounds is
usually concerned with which electronic
transition(s)
a)n __> π*
b)π __> π*
c)n __> σ*
d)σ __> σ*
e)All the above

3. 2. Which of the following wavelength ranges
is associated with UV spectroscopy?
1. 0.8 - 500µm
2. 400 - 100nm
3. 380 - 750nm
4. 0.01 - 10nm

4. 3. Which of the following compounds does
not absorb light in the UV/visible spectrum?
A)Aspirin
B) Paracetamol
C) Chloral hydrate
D)Phenobarbitone

5. 4. A series of 3 colored glass plates of equal thickness are
placed in a light beam. Each sheet absorbs one quarter of the
light incident upon it. What is the intensity of the light
transmitted by the third glass plate?
A) 1.56%
B) 42.19%
C) 56.25%
D) 75.00%

6. 5. Blue light in the visible region has a longer
wave length
A) IR radiation
B) X-rays
C) Microwaves
D) Red light in the visible

7. 6. What is the molar absorptivity of a compound if a 4.4 X 10-5 molar
solution has an absorbance of 0.105 when the path length is 1.0 cm?
A)4.2 X 10-4
B) 1.0 X 108
C) 2.4 X 103
D)4.62 X 10-6

8. 7. The %transmittance of a sample is measured to
be 34%. What will the absorbance be if the
concentration is doubled?
A. 0.94
B. 0.68
C. 0.23
D.0.17

9. 8. UV detector is used in one of the following
methods
A. Gas-Liquid chromatography
B. High Performance liquid chromatography
C. Size Exclusion chromatography
D. Affinity Chromatography

10. 9. The colour of dilute solution of copper sulfate is light blue in
colour, addition of _______ intensifies the colour and shift the
λmax
A. Chlorine
B. Nitrogen
C. Hydrogen
D.Carbon di oxide

11. 10. Which of the following transitions is the highest energy
transition?
a) n __> π*
b) π __> π*
c) n __> σ*
d) σ __> σ*
e) All the above

12. 11. Which of the following alkenes would have
the largest λmax ?

13. 12. Which of the following alkenes would have
the largest λmax?

14. 13. What is the λmax for the following compound?
Use the provided parameters for your calculation.
A. 234
B. 244
C. 273
D. 278
E. 283

15. 14. What is the λmaxfor the following compound?
Use the above parameters for your calculation.
A. 229 nm
B. 249 nm
C. 254 nm
D. 259 nm

16. 15. What is the X and Y axis in this graph?

17. 16. What is the relationship between Absorbance and
Transmittance of a light through a sample in a
Spectophotometer
A. An increase in transmittance usually results in increase in
absorbance
B. An decrease in transmittance usually results in decrease in
absorbance
C. An increase in transmittance usually results in decrease in
absorbance
D. Transmittance and Absorbance should remain equal