Question

Which is the incorrect statement?

• A. Density decreases in case of crystals with Schottky defect
• B. $NaC{l}_{\left(s\right)}$ is an insulator, silicon is a semiconductor, silver is a conductor, quartz is a piezoelectric crystal.
• C. Frenkel defect is favoured in those ionic compounds in which sizes of cations and anions are almost equal.
• D.
  $Fe{O}_{0.98}$ has non-stiochiometric metal deficiency defect.

Answer 1

The correct option is C

Frenkel defect is favoured in those ionic compounds in which sizes of cations and anions are almost equal.

(a) Schottky Defrect $\to$ Equal number of anions and cations are missing No. of ions decreases, volume remains same $\Rightarrow$ Density decreases.

(b) NaCl $\to$ insulator
Silicon $\to$ Semiconductor
Silver $\to$ Conductor
Quartz $\to$ Piezoelectric
Crystal $\to$ Mechanical stress, conducts electricity

(c) Frenkel Defect $\to$ If an ion is missing from lattice site and occupying interstitial site.
Favoured in compounds favoured in compounds in which there is large difference in size of cations and anions with low coordination no.

(d) Non-stoichiometric Defect $\to$ Ratio of cation and anion is different than indicated by ideal chemical formula. .$Fe{O}_{0.98}$