This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Origin of Spectrum”.
1. The analysis of electromagnetic radiation scattered, absorbed or emitted by the molecule is called __________
a) Kaleidoscopy
b) Astronomy
c) Spectroscopy
d) Anatomy
View Answer
Explanation: The analysis of electromagnetic radiation scattered, absorbed or emitted by the molecule is called spectroscopy. Astronomy is the study of celestial objects and processes the physics, chemistry, and evolution of such objects and processes. A kaleidoscope is an optical instrument, typically a cylinder with mirrors containing loose, colored objects such as beads or pebbles and bits of glass. Anatomy is the branch of biology concerned with the study of the structure of organisms and their parts.
2. The energy level with lower energy is called __________
a) Ground state energy level
b) Initial state energy level
c) Excited state energy level
d) All of the mentioned
View Answer
Explanation: The lower energy level is called the ground state and the higher energy level is called excited state. The excited state of a system (such as an atom, molecule or nucleus) is any quantum state of the system that has higher energy than the ground state.
3. Absorption spectrum results when an electron in an atom undergoes a transition from __________
a) Higher energy level to a lower one
b) Lower energy level to a higher one
c) Intermediate levels
d) All of the mentioned
View Answer
Explanation: Absorption spectrum results when an electron in an atom undergoes a transition from lower energy level to a higher one.
4. The energy of a photon is given by __________
a) h/ν
b) ν/h
c) 1/hν
d) hν
View Answer
Explanation: The energy of a photon is given by hν where ν is the frequency and h is plank constant.
5. Select the incorrect statement from the following option.
a) Emission spectrum results when an electron in an atom undergoes a transition from excited state to the ground state
b) In the emission spectrum, transition takes place with the emission of a photon of energy hν
c) In the emission spectrum, transition takes place with the absorption of a photon of energy hν
d) All of the mentioned
View Answer
Explanation: In the emission spectrum, transition takes place with the emission of a photon of energy hν. All the other options are correct. Emission spectrum results when an electron in an atom undergoes a transition from excited state to the ground state.
6. The spectra can be broadly classified into two categories. They are __________
a) Atomic and molecular spectra
b) Atomic and electronic spectra
c) Molecular and electronic spectra
d) None of the mentioned
View Answer
Explanation: The spectra can be broadly classified into two categories: atomic and molecular spectra. Atomic spectra are the spectrum of frequencies of electromagnetic radiation emitted or absorbed during transitions of electrons between energy levels within an atom. Molecular spectra arises from the transition of an electron between the molecular energy levels.
7. In atomic spectroscopy, only electronic transitions are involved.
a) True
b) False
View Answer
Explanation: In atomic spectroscopy, only electronic transitions are involved. It is the spectrum of frequencies of electromagnetic radiation emitted or absorbed during transitions of electrons between energy levels within an atom.
8. Select the correct statement from the following options.
a) Molecular spectra arises from the transition of an electron between the molecular energy levels
b) In molecular transitions, electronic, rotational and vibration transitions occurs
c) Molecular spectra is more complicated than atomic spectra
d) All of the mentioned
View Answer
Explanation: Molecular spectra arises from the transition of an electron between the molecular energy levels. In molecular transitions, electronic, rotational and vibration transitions occurs and molecular spectra is more complicated than atomic spectra.
9. The necessary condition for absorption spectrum is that __________
a) hν should be greater than the energy difference
b) hν should be smaller than the energy difference
c) hν should be equal to the energy difference
d) none of the mentioned
View Answer
Explanation: The necessary condition for absorption spectrum is that hν should be equal to the energy difference(ΔE = Ee – Eg).
10. Spectroscopy deals with the transition that a molecule undergoes on the absorption of suitable radiations determined by quantum mechanical selection rules.
a) True
b) False
View Answer
Explanation: Spectroscopy deals with the transition that a molecule undergoes on the absorption of suitable radiations determined by quantum mechanical selection rules. The spectra can be broadly classified into two categories: atomic and molecular spectra.
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