The pyknometric density of `NaCl` crystal is `2.165 xx 10^(3 kg m^(-3)` while its `X`-ray density is `2.178 xx 10^(-3) kg m^(-3)`. The fraction of unoccupied sites in `NaCl` crystal is
a. `5.96` b. `5.96 xx 10^(-2)`
c. `5.96 xx 10^(-1)` d. `5.96 xx 10^(-3)`

Options

A. `5.96 xx 10^(-1)`
B. `5.96`
C. `5.96 xx 10^(-2)`
D. `5.96 xx 10^(-3)`

Answer

d

Explanation

Difference `= 2.178 xx 10^(3) - 2.165 xx 10^(3) = 0.013 xx 10^(3)`
Fraction unoccupied `= (0.013 xx 10^(3))/(2.173 xx 10^(3)) = 5.96 xx 10^(-3)`