Engineering Physics Multiple Choice Questions on “Classification of Solids”.
1. Which one of the following is the property of an ionic compound?
a) High melting and boiling points
b) Low melting and boiling points
c) Weak inter-atomic forces
d) Non conductors of electricity
Answer: a
Clarification: Ionic compounds are very strong in nature. They require a lot of energy to break them. Therefore they have high melting and boiling points.
2. When do ionic compounds conduct electricity?
a) In gaseous state
b) In solid state
c) When dissolved in water
d) They never conduct
Answer: c
Clarification: Ionic compounds can conduct electricity only if their ions are free to move. Hence they behave as conductors when they are dissolved in water.
3. Which of the following covalent compounds conduct electricity?
a) Silica
b) Graphite
c) Diamond
d) Hydrogen chloride
Answer: b
Clarification: Graphite is made up of carbon layer that can slide over each other. Like metals, the electrons are free to move. Whereas, the rest of the compounds are made up of carbon atoms held together tightly. Therefore, graphite is the covalent compound that conducts electricity.
4. Which of the following is a crystalline solid?
a) Anisotropic substances
b) Isotropic substances
c) Supercooled liquids
d) Amorphous solids
Answer: a
Clarification: Crystalline solids are those in which atoms are arranged in an orderly fashion. They have directional properties and therefore are called anisotropic substances.
5. Why are the glasses of building milky?
a) Because of unwanted deposits
b) Because it becomes old
c) Because it is brittle
d) Because it changes in properties
Answer: d
Clarification: Glasses of the building appear milky because it undergoes heating during the day and cooling during the night. Therefore it acquires some crystalline properties.
6. Which of the following has body centered cubic structure?
a) Polonium
b) Copper
c) Nickel
d) Tungsten
Answer: d
Clarification: In tungsten, atoms are arranged in all eight corners and has an additional atom in the centre satisfying the body centered cubic lattice condition.
7. What is the possible number of different types of lattices (3D)?
a) 4
b) 8
c) 14
d) 17
Answer: c
Clarification: According to Bravis, there are only 14 possible ways of arranging points in space lattice from the 7 crystal systems such that, all the lattice points have exactly the same surrounding.
8. What is the lattice constant for FCC crystal having atomic radius 1.476 Å?
a) 1.476 Å
b) 4.1748 Å
c) 5.216 Å
d) 0
Answer: b
Clarification: Radius=1.476 Å or 1.476 × 10-10 m
Lattice constant for FCC = 4r/√2
Lattice constant = 4.1748 Å.
9. The interplanar spacing of (220) planes of a FCC structure is 1.7458 Å. Calculate the lattice constant.
a) 4.983 Å
b) 2.458 Å
c) 0
d) 5.125 Å
Answer: a
Clarification:
D = 1.7458 Å = 1.7458 × 10-10 m
h = 2; k = 2; l = 0
D=a/√(h2+k2+l2)
a = 4.983 Å.
10. Iron has a BCC structure with atomic radius 0.123 Å. Find the lattice constant.
a) 0
b) 4.587 Å
c) 2.314 Å
d) 0.2840 Å
Answer: d
Clarification: r = 0.123 Å
The lattice constant for BCC = 4r/√3
The lattice constant = 0.2840 Å.