For $NaCl$,the number of Schottky pairs per $cm^3$ at room temperature is

Compounds with low coordination numbers of cations and anions exhibit Frenkel defects because the compound has ................

The pyknometric density of sodium chloride crystal is $2.165 \times 10^3 \ kg \ m^{-3}$ while its $X$-ray density is $2.178 \times 10^3 \ kg \ m^{-3}$. The fraction of unoccupied sites in sodium chloride crystal is

Which type of crystal defect is observed in the diagram given below?
$Na^{+} Cl^{-} Na^{+} Cl^{-} Na^{+} Cl^{-}$
$Cl^{-} \square Cl^{-} Na^{+} \square Na^{+}$
$Na^{+} Cl^{-} \square Cl^{-} Na^{+} Cl^{-}$
$Cl^{-} Na^{+} Cl^{-} Na^{+} \square Na^{+}$

Potassium crystallizes in an $FCC$ lattice with a unit cell edge length of $0.5 \ nm$. The approximate density (in $g \ cm^{-3}$), if it contains $0.1 \%$ Schottky defects, is:

Which of the following does not change the density of $SiC$ solid?