Question

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

• A. $5.96\times10^{-1}$
• B. $5.96\times10^{-3}$
• C. 5.96
• D. $5.96\times10^{-2}$

Answer 1

Answer: (B)

The fraction of unoccupied site in sodium
chloride crystal
$=\frac{X-ray\, density\, - pyknometric\, density}{x-ray\, density}$
$=\frac{2.178\times10^3-2.165\times10^3}{2.178\times10^3}=\frac{0.013\times10^3}{2.178\times10^3}$
$=\frac{13}{2178}=5.96\times10^{-3}$