Question

A unit cell of sodium chloride has four formula units. The edge length of the unit cell is 0.564 nm. What is the density of sodium chloride?

• A. 3.89 g $c{m}^{-3}$
• B. 2.16 g $c{m}^{-3}$
• C. 3 g $c{m}^{-3}$
• D. 1.82 g $c{m}^{-3}$

Answer 1

The correct option is B 2.16 g $c{m}^{-3}$

Theoretical density of crystal, $\rho =\frac{nM}{N_o{a}^3}g/c{m}^3$

For NaCl, $n=4,M=58.5g,a=0.564\times {10}^{-7}cm$

$\therefore \rho =\frac{4\times 58.5}{6.022\times {10}^{23}\times (0.564{)}^3\times {10}^{-21}}=2.16g/c{m}^3$

Hence, the correct option is $\text{B}$