NEET Chemistry The Solid State Questions Solved


(a) What are intrinsic semi-conductors? Give an example.

(b) What is the distance between Na+ and Cl- ions in NaCl crystal if its density is 2.165 g cm-3? [Atomic mass of Na = 23u, Cl = 35.5u; Avogadro's number = 6.023×1023]

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Concept Questions :-

Density/Formula/packing fraction/ Semiconductors

(a) Intrinsic semi-conductors : These are insulators at room temperature and become semi-conductors when temperature is raised, Example : silicon and germanium.

(b) Applying the formula

ρ = ZMa3×NA, Z for NaCl is 4(fcc)

or a3ZMρ×NA = 4×58.52.165×6.023×1023

a = 4×58.52.165×6.023×10233 = 564×10-10 cm

a = 2× distance between Na+ and Cl- ions

 Distance between Na+ and Cl- ion

564×10-102  = 282 pm.

Difficulty Level:

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