The pyknometric density of sodium chloride crystal is `2.165xx10^(3)kg m^(-3)` while its `X` ray density is `2.178xx10^(3)kg m^(-3)` the fraction of unoccupied sites in `NaCl` crystal is

Options

A. 5.96
B. `5.96xx10^(-2)`
C. `5.96xx10^(-1)`
D. `5.96xx10^(-3)`

Answer

D

Explanation

Molar volume from pyknometric density =`M/(2.165xx10^3)m^3`
Molar volume from X-ray density `=M/(2.178xx10^3)m^3`
`therefore` Volume unoccupied `=M/10^3(1/2.165-1/2.178)m^3=(0.013Mxx10^(-3))/(2.165xx2.178)`
`therefore` Fraction unoccupied `=((0.013Mxx10^(-3))/(2.165xx2.178))//((Mxx10^(-3))/2.165)=5.96xx10^(-3)`