Question

Calculate the number of molecules of sulphur $\left(S_8\right)$ present in 16 g of solid sulphur. [2 marks]

Answer 1

1 mole of solid sulphur $\left(S_8\right)$ = 8 x 32 g = 256 g [0.5 mark]
i.e., 256 g of solid sulphur contains $=6.023\times {10}^{23}$ molecules
Then, 16 g of solid sulphur contains $=\frac{6.023\times {10}^{23}}{256}\times 16$ molecules. [1.0 mark]
$=3.76\times {10}^{22}$ molecules [0.5 mark]