This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Spectroscopy”.
1. What is molecular spectroscopy?
a) Change in energy at atomic level
b) Change in energy at molecular level
c) Change in energy at visible level
d) No change in energy
View Answer
Explanation: Molecular spectroscopy involves the interaction of electromagnetic radiation with materials in order to produce an absorption pattern from which structural or compositional information can be deduced. This also involves change in energy at molecular level.
2. In which of the following spectroscopy, EMR are not used?
a) Atomic spectroscopy
b) Molecular spectroscopy
c) Mass spectroscopy
d) Infrared spectroscopy
View Answer
Explanation: Mass spectroscopy is not based on electromagnetic radiations therefore, EMR are not used in mass spectroscopy. In this technique, light is not being measured after inserting the sample and ionizing the molecules which are separated by mass to charge ratios.
3. Which of the following wavelength ranges is associated with UV spectroscopy?
a) 0.9-500μm
b) 410-99nm
c) 390-740nm
d) 0.02-9nm
View Answer
Explanation: The following table shows the wavelengths and their associated spectroscopies.
| Wavelength | Spectroscopy |
|---|---|
| 0.9-500μm | IR spectroscopy |
| 390-740nm | Visible spectroscopy |
| 0.02-9nm | X-ray range spectroscopy |
| 410-99nm | UV spectroscopy |
Therefore, UV spectroscopy has the wavelength ranges 410-99nm.
4. Which of the following does not absorb light in the UV/visible spectrum?
a) Aspirin
b) Paracetamol
c) Chloral hydrate
d) Phenobarbitone
View Answer
Explanation: In order to absorb light in the UV/visible spectrum, a molecule must possess a chromophore, example a benzene ring or conjugated double bonds. Chloral hydrate does not possess a chromophore and therefore, cannot absorb light in the UV/visible spectrum.
5. Which of the following frequency range is known as the fingerprint region in infrared spectroscopy?
a) 400-1400 cm-1
b) 1400-900 cm-1
c) 900-600 cm-1
d) 600-250 cm-1
View Answer
Explanation: The fingerprint region of an infrared spectroscopy, which is characterized for each individual compound, is between 1400 and 900 cm-1. Therefore, this range is known as the fingerprint region in infrared spectroscopy.
6. Which of the following cannot be the property of gas chromatography?
a) Color Estimation
b) Drugs Estimation
c) Raw material characterization
d) Study of intravenous NaCl infusion
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Explanation: In order to be analyzed by gas chromatography, compounds must be able to be easily volatilized. Volatile oils, drugs, metabolites and raw materials for drug synthesis are all relatively volatile. Sodium chloride is not volatile and hence, it cannot be assayed by gas chromatography.
7. Which of the following statement is correct?
a) Wavelength is directly proportional to wavenumber
b) Wavenumber is directly proportional to energy
c) Wavelength is directly proportional to frequency
d) Wavelength is directly proportional to energy
View Answer
Explanation: The energy content E of photons is inversely proportional to the wavelength of the electromagnetic wave according to the following equation:
E = h.v = h (c/λ).
As you know, wavenumber is (1/λ), hence it is directly proportional to energy.
8. Which of the following statement is correct?
a) Ultraviolet radiation has a longer wavelength than infrared radiation
b) Microwave radiation possesses more energy than infrared radiation
c) Infrared radiation has a shorter wavelength than visible light
d) Infrared radiation has a lower wavenumber than visible light
View Answer
Explanation: Infrared spectroscopy has wavenumber in the range 40-13000 cm-1 whereas visible light has wavenumber in the range 12500-25000 cm-1. Therefore, infrared radiation has a lower wavenumber than visible light.
9. Energy of EMR is calculated by the equation, E=hv.
a) True
b) False
View Answer
Explanation: Energy of EMR is calculated by the equation E = hv, where, ‘E’ is the energy of radiation, ‘h’ is the Plank’s constant and ‘v’ is the frequency of radiation. EMR is made up of discrete particle called as photons. It has both particle and wave characteristics.
10. Why colorimeter is used to measure the absorbance of a colored compound in a solution?
a) It is very low in terms of detecting
b) It does not cause the light wave to move
c) It measures the particular wavelength of light
d) Colorimeter is not used to measure the colored compound
View Answer
Explanation: A colorimeter is a device used in colorimetry that measures the absorbance of particular wavelengths of a light by a specific solution. It is commonly used to determine the concentration of a known solute in a given solution by the application of Beer-Lambert law.
Sanfoundry Global Education & Learning Series – Physical Chemistry.
To practice all areas of Physical Chemistry, here is complete set of Multiple Choice Questions and Answers.
