The molar mass of water ($\text{H}_2\text{O}$) is approximately $18 \text{ g mol}^{-1}$ . Given that the density of water is $1 \text{ g cm}^{-3}$, we can calculate the volume occupied by one mole of water: $\text{Volume} = \frac{\text{Mass}}{\text{Density}}$ $\text{Volume of } 1 \text{ mole} = \frac{18 \text{ g}}{1 \text{ g cm}^{-3}} = 18 \text{ cm}^3$. One mole of water contains Avogadro's number of molecules ($N_A = 6.022 \times 10^{23}$) . Therefore, the volume occupied by a single water molecule is: $\text{Volume of one molecule} = \frac{\text{Volume of one mole}}{N_A}$ $\text{Volume of one molecule} = \frac{18 \text{ cm}^3}{6.022 \times 10^{23}} \approx 2.989 \times 10^{-23} \text{ cm}^3 \approx 3.0 \times 10^{-23} \text{ cm}^3$.