Question

NaH crystallizes in the same structure as that NaCl. The edge length of the cubic unit cell of NaH is $4.88\mathring{A}$ , then calculate the density (in g cm${}^{-3}$) of NaH.

• A. $1.7$
• B. $2.8$
• C. $1.4$
• D. $2.4$

Answer 1

The correct option is C $1.4$

As we know, the expression for density is as follows:

Density $=d=\frac{nM}{V{N}_o}$ ( where $n$ is the number of atoms per unit cell )

For NaH, we have $n=4$

Density $=d=\frac{4\times 24}{(4.88\times {10}^{-10}{)}^3(6\times {10}^{23})}=1.4$ g cm${}^{-3}$

Hence, the correct option is C.