Problem 105P

A drop of water has a volume of approximately 0.05 mL. How many water molecules does it contain? (density of water = 1.0 g/cm3)

Solution 105P

The volume of one drop of water = 0.05 mL

It is known that the density of water is one, the mass is 0.05g. The molar mass of water is 18.0g/mol.

This means there is one mole of water in 18.0gm.

One mole = 6.02 1023 molecules.

Then the conversion of grams into number of atoms = 0.05 g 18.0g 6.02 1023 molecules

= 1.67 1021 molecules.