Calculate the number of molecules of sulphur$\left(S_8\right)$ present in $16g$ of solid sulphur.

We have to find the number of molecules present in 16g of solid sulphur.

The molecular mass of the sulphur molecule is 32 × 8 = 256 u.

1 mole of sulphur molecules is equal to 256 grams.

This means 256 g of solid sulphur contains = 6.022 x ${10}^{23}$ molecules.

Then, 16 g of solid sulphur contains =6.022 x ${10}^{23}$ / 256 $\times$ 16 molecules

= 3.76375 x ${10}^{22}$ molecules

Therefore, 16 g of $S_8$ contains 3.76 x ${10}^{22}$ molecules.