This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Spectroscopy – Set 2”.
1. According to the Beer-Lambert law, on which of the following absorbance does not depend?
a) Extinction coefficient of the sample
b) Color of the solution
c) Distance that the light has travelled through the sample
d) Solution concentration
View Answer
Explanation: According to the Beer-Lambert law, absorbance depends on the extinction coefficient of the sample, length or distance of the path light travelled and concentration of the solution. It does not depend upon the color of the solution.
2. The frequency of a transition wave is 4.5×1015 Hz. What is the corresponding wavelength?
a) 560 nm
b) 6.0×10-6 m
c) 6.7×10-8 m
d) 180000 cm-1
View Answer
Explanation: The relationship between frequency and wavelength is, c = λv
where, c is the speed of the light, λ
is the wavelength and v is frequency. Therefore,
c = λv = λ = c/v= λ = 3×108/4.5×1015 = 6.7×10-8 m. The wavelength is 5.6×10-8 m.
3. A transition has a wavenumber of 2000 cm-1. In what part of the electromagnetic spectrum does this lie?
a) Radiowave
b) Electrostatic
c) Magnetic
d) Infrared
View Answer
Explanation: The wavenumber range of infrared spectrum is 40 to 13,000 cm-1. Therefore, the transition with wavenumber 2000 cm-1 lies in infrared spectrum. Infrared radiations have wavelengths longer than visible light.
4. Absorption has a wavelength of 495 nm. In what part of the electromagnetic spectrum does this lie?
a) IR waves
b) Magnetic waves
c) Electrostatic
d) Ultraviolet-visible
View Answer
Explanation: The wavelength range of ultraviolet-visible is between 200 to 800 nm. Therefore, the wavelength of absorption with 495 nm lies in ultraviolet-visible region. Absorption of visible and ultraviolet radiation is associated with excitation of electrons.
5. The frequency of a transition is 3.1×1010 Hz. What is the energy of this transition?
a) 4.3×10-44 J
b) 5.4×10-44 KJ
c) 33.4×10-23 KJ
d) 3.4×10-23 J
View Answer
Explanation: The relationship between frequency and energy is, E= hv where, E is the energy of the transition in J, h is the Planck’s constant = 6.626×10-34 Js and v is frequency in Hz. Therefore,
E = hv
E = 6.626×10-34 × 5.1×1010 = 3.4×10-23 J. The energy is 2.0×10-23 J.
6. What is the classification of spectroscopy on the basis of working principle of absorption of radiation?
a) UV spectroscopy
b) IR spectroscopy, UV spectroscopy
c) UV spectroscopy, IR spectroscopy, Colorimetery
d) Colorimetery
View Answer
Explanation: On the basis of the working principle of absorption of radiation, spectroscopy is classified into three types. These are UV (Ultraviolet-visible) spectroscopy, IR (Infrared) spectroscopy and colorimetry.
7. What is the classification of spectroscopy on the basis of working principle of emissions of radiation?
a) Flame photometry, fluorimetry
b) Fluorimetry
c) UV spectroscopy, IR spectroscopy, NMR
d) IR spectroscopy, ESR
View Answer
Explanation: On the basis of the working principle of emissions of radiations, spectroscopy is classified into two types. These are flame photometry and fluorimetry. Fluorimetry is a technique used to measure the parameters of visible light and flame photometry is the inorganic chemical analysis used to determine the concentration of certain metal ions.
8. What is the classification of spectroscopy on the basis of working principle of change in EMR due to change in magnetic level?
a) ESR, EMR
b) NMR, DSR
c) ESR, NMR
d) IR
View Answer
Explanation: On the basis of the working principle of change in EMR due to change in magnetic level, spectroscopy is classified into three types. These are ESR (Electron paramagnetic resonance) and NMR (Nuclear magnetic resonance).
9. What is the classification of spectroscopy on the basis of change of energy?
a) Atomic spectroscopy, ESR, NMR
b) Molecular spectroscopy, atomic spectroscopy
c) NMR, ESR
d) IR, UV
View Answer
Explanation: On the basis of change of energy, spectroscopy is classified into two types. These are molecular spectroscopy and atomic spectroscopy. Molecular spectroscopy involves change in energy at molecular level and atomic spectroscopy involves change in energy at atomic level.
10. What is atomic spectroscopy?
a) Change in energy at atomic level
b) Change in energy at photon level
c) Change in energy at electron level
d) Change in energy at molecular level
View Answer
Explanation: Atomic spectroscopy is the study of the electromagnetic radiation absorbed and emitted by atoms. It is primarily used for the determination of trace metals in many types of samples composed of organic or inorganic matrices. It involves change in energy at atomic level.
Sanfoundry Global Education & Learning Series – Physical Chemistry.
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