31. Which of the following is a type of defect found in ionic crystals where both cations and anions leave their lattice sites?
a) Frenkel defect
b) Vacancy defect
c) Schottky defect
d) Interstitial defect
Answer:
c) Schottky defect
Explanation:
A Schottky defect occurs in ionic crystals when equal numbers of cations and anions leave their lattice sites, creating vacancies. This defect reduces the density of the solid but maintains electrical neutrality.
32. Which of the following is a characteristic of amorphous solids?
a) Sharp melting points
b) Long-range order
c) Definite geometric shapes
d) Irregular arrangement of particles
Answer:
d) Irregular arrangement of particles
Explanation:
Amorphous solids lack a long-range ordered structure. Their particles are arranged randomly, unlike crystalline solids, which have a regular and repeating pattern. Amorphous solids do not have sharp melting points; they soften over a range of temperatures.
33. Which of the following shows metallic bonding?
a) Sodium chloride
b) Copper
c) Diamond
d) Ice
Answer:
b) Copper
Explanation:
Copper exhibits metallic bonding, where positive metal ions are surrounded by a “sea” of delocalized electrons that allow for high electrical and thermal conductivity. This contrasts with ionic bonding in sodium chloride or covalent bonding in diamond and ice.
34. What is the coordination number in a body-centered cubic (BCC) structure?
a) 4
b) 6
c) 8
d) 12
Answer:
c) 8
Explanation:
In a body-centered cubic (BCC) structure, each atom at the center of the cube is surrounded by 8 nearest neighbors at the corners of the cube, giving a coordination number of 8.
35. Which of the following solids conducts electricity due to the movement of electrons?
a) Ionic solids
b) Covalent network solids
c) Molecular solids
d) Metallic solids
Answer:
d) Metallic solids
Explanation:
Metallic solids conduct electricity due to the presence of free-moving delocalized electrons within the “sea of electrons.” In ionic solids, conduction occurs via ions in the molten state, while covalent network and molecular solids are generally poor conductors.
36. In which type of crystal defect do smaller ions occupy interstitial spaces in the crystal lattice?
a) Schottky defect
b) Vacancy defect
c) Interstitial defect
d) Frenkel defect
Answer:
c) Interstitial defect
Explanation:
In an interstitial defect, smaller atoms or ions occupy the spaces (interstices) between the regular lattice points. This type of defect increases the density of the crystal.
37. Which of the following has a hexagonal close-packed (hcp) structure?
a) Sodium
b) Iron
c) Zinc
d) Gold
Answer:
c) Zinc
Explanation:
Zinc has a hexagonal close-packed (hcp) structure, where the atoms are arranged in a hexagonal pattern with two layers of close-packed atoms. This structure has a coordination number of 12.
38. Which of the following types of solids is the best conductor of heat and electricity?
a) Ionic solid
b) Molecular solid
c) Metallic solid
d) Covalent network solid
Answer:
c) Metallic solid
Explanation:
Metallic solids are the best conductors of heat and electricity because of the presence of delocalized electrons that can move freely throughout the solid. These free electrons facilitate the conduction of electricity and heat.
39. Which of the following defects does not affect the density of the solid?
a) Schottky defect
b) Frenkel defect
c) Interstitial defect
d) Vacancy defect
Answer:
b) Frenkel defect
Explanation:
In a Frenkel defect, a smaller ion (usually a cation) leaves its normal lattice site and occupies an interstitial site. Since no ions are lost or gained, the overall density of the solid remains unchanged.
40. What is the type of bonding in diamond?
a) Metallic bonding
b) Ionic bonding
c) Covalent bonding
d) Hydrogen bonding
Answer:
c) Covalent bonding
Explanation:
Diamond consists of carbon atoms bonded covalently in a tetrahedral arrangement, forming a three-dimensional network. Each carbon atom is covalently bonded to four other carbon atoms, resulting in a very hard and strong structure.
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