Question

The compound CuCl has ZnS (ccp) structure. Its density is $3.4$ g cm${}^{-3}$. What is the length of the edge of the unit cell?

• A. 5.78 cm
• B. 578 pm
• C. 587 m
• D. None of these

Answer 1

Answer: (B)

578 pm

The expression for the density of the unit cell is given below.

$d=\frac{n\times m}{a^3\times N_A}$

$d=3.4$ g cm${}^{-3}$

$n=4$

$m=97.5$ g/mol

Substituting values in the above expression, we get

$3.4=\frac{4\times 97.5}{(a{)}^3\times 6.023\times {10}^{23}}$ $⟹a^3=1.9\times {10}^{-22}$ $⟹a=5.78\times {10}^{-8}$ cm $=578$ pm

Hence, the edge length of the unit cell is $578$ pm.