Which is the incorrect statement ?

Options

A. `FeO_0.98` has non-stoichiometric metal deficiency defect
B. Density decreases in case of crystals with Schottky's defect
C. NaCl(s) is insulator , silicon is semiconductor, silver is conductor , quartz is piezoelectric crystal
D. Frenkel defect is favoured in those ionic compounds in which the sizes of cations and anions are almost equal

Answer

A,D

Explanation

Non-stoichiometric ferrous oxide is `Fe_(0.93-0.98) O_1.00` ( and not `FeO_0.98`) which is due to metal deficiency defect. Hence, (a) is incorrect. Frenkel defect is favoured in those ionic compounds in which sizes of cation and anion are largely different . Hence (d) is incorrect.