Question

An element occurs in the body centred cubic lattice with cell edge of $300$ pm. The density of the element is $8.0$ g cm${}^{-3}$. The atomic mass of the element is:

• A. $65$
• B. $60$
• C. $52$
• D. $80$

Answer 1

The correct option is A $65$

The expression for density is given below:

$d=\frac{zM}{N_A{a}^3}$

Here, $d=$ density $=8,z$ for bcc $=2,a=300pm=300\times {10}^{-10}cm.$

Putting these values in the above equation,

$8=\frac{2\times M}{6.023\times {10}^{23}\times (300\times {10}^{-10}{)}^3}$

$⟹M=65$

Hence, the atomic mass of the element is $65$ g/mol.