Due to vacancy defects,the density of a solid substance .............

Analysis of the density of an electrically neutral $NaCl$ crystal containing vacancies yielded the following results:
$(i)$ Density of $NaCl$ crystal with all sites occupied $= 2.178 \times 10^3 \ kg \ m^{-3}$
$(ii)$ Density of $NaCl$ crystal with vacancies $= 2.165 \times 10^3 \ kg \ m^{-3}$
Then the percentage of vacancies in the $NaCl$ crystal is .....

Schottky defect in a crystal arises due to

What kind of defects do most ionic crystals possess?

What type of stoichiometric defect is shown by:
$(i)$ $ZnS$
$(ii)$ $AgBr$

Which one of the following has Frenkel defect?