Question

The number of unit cells in $58.5g$ of $NaCl$ is nearly:

• A. $6\times {10}^{22}$
• B. $3\times {10}^{22}$
• C. $1.5\times {10}^{23}$
• D. $0.5\times {10}^{24}$

Answer 1

The correct option is C $1.5\times {10}^{23}$

The molar mass of NaCl is $\Rightarrow 23+35.5=58.5g$.

Thus, 58.5 g of NaCl corresponds to 1 mole of NaCl and contains $6.023\times {10}^{23}$ molecules.

One unit cell of NaCl (fcc structure) has 4 NaCl molecules. Hence, 1 mole of NaCl will contain $\frac{6.023\times {10}^{23}}{4}\approx 1.5\times {10}^{23}$ unit cells.

The number of unit cells in $58.5$ g of NaCl is nearly $1.5\times {10}^{23}.$

Hence, option C is correct.