Engineering Chemistry Questions and Answers – Vibrational Spectroscopy

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This set of Engineering Chemistry Online test focuses on “Vibrational Spectroscopy”.

1. Vibrational spectroscopy involves the transitions falling in the spectral range of ____________
a) 100-1000 cm-1
b) 300-3000 cm-1
c) 400-4000 cm-1
d) 500-5000 cm-1
View Answer

Answer: c
Explanation: Vibrational spectroscopy involves the transitions falling in the spectral range of 400-4000 cm-1 (infrared region).

2. Which of the region of IR spectra appears between (1400-600) cm-1?
a) Functional group region
b) Fingerprint region
c) Low-frequency region
d) None of the mentioned
View Answer

Answer: b
Explanation: Fingerprint region of IR spectra appears between (1400-600) cm-1.

3. Select the correct statement from the following option.
a) Infrared spectra can identify the unknown materials
b) It can determine the amount of components in a mixture
c) It can also determine the quality of a sample
d) All of the mentioned
View Answer

Answer: d
Explanation: Infrared spectra can identify the unknown materials. It can determine the amount of components in a mixture and can also determine the quality of a sample.
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4. Which of the following molecule have infrared active vibrations?
a) NO
b) CH4
c) H2
d) All of the mentioned
View Answer

Answer: a
Explanation: NO molecule have infrared active vibrations. Infrared spectra can identify unknown materials. It can determine the amount of components in a mixture and can also determine the quality of a sample.

5. Which of the following cannot show a vibrational absorption spectrum?
a) OCS
b) H2O
c) CO2
d) C H2 = C H2
View Answer

Answer: d
Explanation: C H2 = C H2 cannot show vibrational absorption spectrum. OCS, H2O and CO2 can show a vibrational absorption spectrum.
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6. Which of the following is not a type of bending molecular vibration?
a) Twisting
b) Stretching
c) Wagging
d) Rocking
View Answer

Answer: b
Explanation: Stretching is not a type of bending molecular vibration. Twisting, wagging and rocking are types of bending molecular vibration.

7. What is the absorption frequency(cm-1) of –C=N functional group?
a) 3610-3640
b) 1690-1760
c) 1180-1360
d) 2850-2960
View Answer

Answer: c
Explanation: The absorption frequency for –C=N group is 1180-1360 cm-1. Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample.
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8. Presence of a functional group in a compound can be established by using _____________
a) Chromatography
b) IR spectroscopy
c) Mass spectroscopy
d) X-ray diffraction
View Answer

Answer: b
Explanation: Presence of a functional group in a compound can be established by using IR spectroscopy. It is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light.

9. Select the incorrect option from the following option.
a) IR spectroscopy helps in the determination of purity
b) IR spectroscopy helps in the determination of force constant from vibrational spectrum
c) IR spectroscopy helps in identifying an unknown compound
d) None of the mentioned
View Answer

Answer: d
Explanation: All the options are correct. IR spectroscopy helps in the determination of purity, force constant from the vibrational spectrum and identifying an unknown compound.
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10. IR spectroscopy helps in detecting the presence of hydrogen bonding.
a) True
b) False
View Answer

Answer: a
Explanation: IR spectroscopy helps in detecting the presence of hydrogen bonding. It is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light.

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