PPSC Chemistry Lecturer Preparation (Test # 16)- Malik Xufyan 03137355727

1. PPSC CHEMISTRY CLASS
Test Session
Chapter: Ultra Visible Spectroscopy
Test No. 16
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1. What is the wavelength range for UV spectrum of light?
a) 400 nm – 700 nm
b) 700 nm to 1 mm
c) 0.01 nm to 10 nm
d) 10 nm to 400 nm
2. Which of the following comparison is correct for solvent shift on the n –>π* transition
of acetone?
a) H20 = CH30H = C2H50H = CHC13 = C6H14
b) H20 > CH30H > C2H50H > CHC13 > C6H14
c) H20 < CH30H < C2H50H < CHC13 < C6H14
d) H20 > CH30H < C2H50H < CHC13 < C6H14
3. What is the correct order of λmax for n –> σ* transition?
a) R-OH > R-NH2 > R-SH
b) R-OH < R-NH2 < R-SH
c) R-OH > R-SH > R-NH2
d) R-OH < R-SH < R-NH2
4. What is the correct order of λmax for n –> π* transition for the R-CN, R-NO2, and R-
N=N-R?
a) R-CN < R-NO2 < R-N=N-R
b) R-CN = R-NO2 = R-N=N-R
c) R-CN > R-NO2 > R-N=N-R
d) R-CN > R-NO2 < R-N=N-R
5. What is the correct order of λmax for π –> π* transition for the following three com-
pounds?
a) R-C=C-R > R2C = CR2 > R-CHO
b) R-C=C-R < R2C = CR2 < R-CHO
c) R-C=C-R = R2C = CR2 = R-CHO

2. d) R-C=C-R < R2C = CR2 >R-CHO
6. What is the correct order of λmax for n–> π* transition for the following three com-
pounds?
a) RCOOH > RCOOR’ > RCONH2
b) RCOOH = RCOOR’ = RCONH2
c) RCOOH = RCOOR’ < RCONH2
d) RCOOH = RCOOR’ > RCONH2
7. Which of the following is the correct order of λmax for n–> π* transition for the given
compounds?
a) 1>2>3>4>5
b) 1<2<3<4<5
c) 1>2<3>4<5
d) 1>2>3<4>5
8. The ultraviolet spectrum of benzonitrile shows a primary absorption band at 224 nm. If
a solution of benzonitrile in water, with a concentration of 1x 10-4 molar, is examined at a
wavelength of 224 nm, the absorbance is determined to be 1.30. The cell length is 1 cm.
What is the molar absorptivity of this absorption band?
a) 2.3 x 104
b) 3.3 x 104
c) 1.3 x 104
d) 4.3 x 104
9. The ultraviolet spectrum of benzonitrile shows a secondary absorption band at 271 nm.
If a solution of benzonitrile in water, with a concentration of 1×10-4 molar solution is ex-
amined at 271 nm, what will be the absorbance reading (ℇ = 1000) and what will be the
intensity ratio, IO/I, respectively?
a) 0.1, 1.26
b) 0.2, 2.26
c) 0.3, 3.26

3. d) 0.4, 4.26
10. Which of the following structural formula that is consistent with the following obser-
vations: An acid, C7H4O2Cl2 shows a UV maximum of 242 nm?
a)
b)
c)
d)
11. In which region of the electromagnetic spectrum does an absorption at 600 nm come?
a) Infrared.
b) Visible.
c) Vacuum-UV.
d) Near -UV.
12. A solution of 0.001 mol dm–3 NiSO4 is placed in an optical cell of pathlength 1 cm,
and the absorption spectrum is recorded. The absorptions have characteristic
λmax and εmax values. What are the correct units of εmax?
a) cm mol dm–3
b) dm3 mol–1 cm–1
c) cm dm3 mol–1

4. d) mol dm–3 cm–1
13. In which region of the electromagnetic spectrum does an absorption at 177 nm
come?
a) Near -UV.
b) Visible.
c) Infrared.
d) Vacuum-UV.
14. What does the notation σ*←n mean?
a) Absorption; transition from a quantum level n to σ* MO.
b) Absorption; transition from a non-bonding MO to σ* MO.
c) Emission; transition from a quantum level n to σ* MO.
d) Emission; transition from a non-bonding MO to σ* MO.
15. How do values of λmax for the π*←π transitions vary among a series of conjugated
polyenes?
a) Values shift to shorter wavelength as the number of C=C double bonds increases.
b) Values vary but in no particular pattern.
c) Values shift to longer wavelength as the number of C=C double bonds increases.
d) Values vary very little.
16. What is a red shift?
a) The shifting of an absorption to shorter wavelength.
b) The shifting of an absorption to higher energy.
c) The shifting of an absorption to lower energy.
d) The shifting of an absorption towards the blue end of the spectrum
17. What is a chromophore?
a) A coloured compound.
b) A group of atoms in a coloured compound.
c) A group of atoms in a compound responsible for electromagnetic radiation.
d) A group of atoms in a compound responsible for the absorption of electromagnetic
radiation.
18. Which of the following is the principal chromophore in an azo-dye?
a) N≡N
b) C=N
c) N=N
d) C≡N

5. 19. Lycopene (λmax = 469 nm) is present in tomatoes. What colour of light does
lycopene absorb?
a) Green.
b) Red.
c) Blue.
d) Orange.
20. In which of the following are the π-electrons not delocalized?
a) An α,β-unsaturated ketone.
b) Hepta-1,6-diene.
c) Buta-1,3-diene.
d) Allyl anion.
21. All but one of the following groups can donate a lone pair of electrons into the
carbon π- system of a conjugated polyene. Which is the odd one out?
a) OMe
b) SMe
c) NMe2
d) Me
22. Which statement is incorrect about the allyl anion and buta-1,3-diene?
a) Both have four π MOs.
b) Both have four π-electrons.
c) In both, the C atoms are all sp2 hybridized.
d) In both, the π-bonding is delocalized.

6. 23. Which of the following arrangements of carbon-carbon double bonds along the
backbone of a polyene does not correspond to a conjugated system?
a) –C=C–C=C–
b) –C=C–C=C–C=C–
c) –C=C–C–C=C–
d) –C=C–C=C–C=C–C=C–
24. An aqueous solution of a dye has a strong absorption with λmax= 464 nm. The
colour of the solution is:
a) colourless.
b) orange.
c) green.
d) purple.
25. Which of the following absorption maxima is not in the visible range of the
electronic spectrum?
a) λmax = 750 nm
b) λmax = 250 nm
c) λmax = 550 nm
d) λmax = 480 nm
26. Which of the following statements is consistent with an electronic absorption being
broad?
a) An electronic absorption includes vibrational and rotational structure.
b) Hydrogen bonding causes an electronic absorption to be broad.
c) The absorption of a photon is slower than the timescale of molecular vibrations.
d) Electronic transitions are always localized on a single atomic centre.

7. 27. Two solutions of the same compound were made up. Solution A was of
concentration 0.98 × 10–4 mol dm–3, and solution B was 1.66 × 10–2 mol dm–3.
The electronic spectrum of solution A contained one absorption at λmax = 230 nm,
while the spectrum of solution B contained absorptions at λmax = 230 and 365 nm.
The difference in the spectra was because:
a) the value of λmax depends on concentration.
b) electronic spectroscopic data are not always reproducible.
c) the value of εmax depends on concentration.
d) εmax for the absorption at 365 nm is much smaller than εmax of the band at 230 nm.
28. A compound X is characterized in its electronic spectrum by an absorption with
λmax = 217 nm (εmax = 21 000 dm3 mol–1 cm–1). Of the compounds given below,
X is most likely to be:
a) water.
b) ethanol.
c) buta-1,3-diene.
d) β-carotene.

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