This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Hydrogen Bonds, Hybrid Orbitals, and Band Theory of Solids – Set 2”.
1. Which of the following is energy difference between conduction band and valence band?
a) Forbidden band
b) Valence band
c) Conduction band
d) Empty band
View Answer
Explanation: The amount of energy required to move an electron from valence band to conduction band is called forbidden energy gap or forbidden band. Thus, forbidden gap is the difference of energy levels of conduction band and valence band.
2. Which of the following is a band partially filled with electrons?
a) Core band
b) Conduction band
c) Forbidden band
d) Valence band
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Explanation: A conduction band is a band that is partially filled with electrons. Electrons move from valence band to conduction band. These electrons are very active and are also responsible for electrical conductivity.
3. Where does one atom or molecule lie in a simple cube?
a) Five corners
b) Nine corners
c) Six corners
d) Eight corners
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Explanation: The smallest repeating unit of a crystal lattice is called the unit cell. The simple cubic unit cell contains only eight atoms, molecules or ions at the corners of a cube. Thus, a single unit cell can clam only 1/8 of each of eight atoms.
4. Which of the following is satisfactorily explained by the band theory?
a) Electrical insulators only
b) Electrical conductors only
c) Electrical semi-conductors only
d) Electrical insulators, electrical conductors and electrical semi- conductors
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Explanation: The electrical insulators, electrical conductors and electrical semi-conductors are easily explained by the band theory of solids. Band theory uses the molecular orbitals of a solid to explain these phenomena.
5. Homogeneity is used to describe the density of atoms in a direction.
a) True
b) False
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Explanation: Homogeneity is used to describe the density of atoms remains same along any direction in a crystal. Homogenous nucleation can only become viable if the strain energy and surface energy involved in creating a crystal are small.
6. Which of the following is the name given to the materials in which valence electrons are tightly bound to their atoms at low temperature?
a) Semi-conductor
b) Super conductors
c) Insulators
d) Conductors
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Explanation: Most solid materials are classified as insulators because they offer very large resistance to the flow of electric current. In most materials, even the outermost electrons are so tightly bound so there is essentially zero electron flow and these materials are classified as insulators.
7. Which of the following is opposed by coercive force?
a) Extension
b) Surface cracking
c) Breakage
d) Demagnetization
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Explanation: Demagnetization is opposed by coercive force. Coercive force measures the ability of a ferromagnetic material to withstand an external magnetic field, without being demagnetized. It is also called by the names coercivity or coercive field.
8. Which of the following property states that the angular position of cells remains the same for a sample of a crystal?
a) Isotropy
b) Cleavage
c) The external symmetry of form
d) Homogeneity
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Explanation: The external symmetry of form states that the angular position of cells remains the same for a sample of crystal. The symmetry in the crystals is due to the regular arrangement of atoms or molecules.
9. Which of the following is defined by the breaking of crystals along definite direction?
a) Homogeneity
b) Cleavage
c) Isotropy
d) Symmetry
View Answer
Explanation: Cleavage is the tendency of a material to break along certain planes. When a material breaks along a plane it makes a smooth surface. The shapes form as the materials are broken along their cleavage planes.
Sanfoundry Global Education & Learning Series – Physical Chemistry.
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