Test: Classification Of Solids - Mechanical Engineering MCQ

 Ionic compounds are very strong in nature. They require a lot of energy to break them. Therefore they have high melting and boiling points.

 Ionic compounds can conduct electricity only if their ions are free to move. Hence they behave as conductors when they are dissolved in water.

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.

Crystalline solids are those in which atoms are arranged in an orderly fashion. They have directional properties and therefore are called anisotropic substances

Glasses of building appear milky because it undergoes heating during the day and cooling during night. Therefore it acquires some crystalline properties

 In tungsten, atoms are arranged in all eight corners and has an additional atom in the centre satisfying the body centred cubic lattice condition.

 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.

Radius=1.476 Å or 1.476 × 10^-10 m
Lattice constant for FCC = 4r/√2
Lattice constant = 4.1748 Å

D = 1.7458 Å = 1.7458 × 10^-10 m
h = 2; k = 2; l = 0
D=a/√(h²+k²+l²)
a = 4.983 Å

 r = 0.123 Å
The lattice constant for BCC = 4r/√3
The lattice constant = 0.2840 Å