Volume of drop of water = 1.0 mL
Density of water = 1.0 g/mL
∴ Mass of drop of water = Volume × Diabesity = 1.0 g
Molecular mass of H2O = 2 × 1 u + 1 × 16 u = 18 u
Gram molecular mass of water = 18 g/mol
18 g of water contains = 6.022 × 1023 molecular
∴ 1 g of water contains = (6.022 × 1023 / 18) molecular
= 3.34 ×1022 molecules.