Question

calculate the number of water molecules in a liter of water. Assume the density of water to be 1kg/dm^3

Answer 1

By mole concept, we know that 1 mole molecule of any substance has avogadro number of molecules(6.022*10^23).

So we need to find the moles of water in 1 L of water or 1000mL of water. Taking the density of water to be 1g/mL, 1000mL of water= 1000g water.

Therefore, number of moles= given mass of water(1000)/molecular mass of water(18)

Moles =1000/18= 55.55

So total molecules in 55.55 moles= 55.55* 6.022*10^23 = 334.52*10^23 molecules

=3.34*10^25 molecules of water.