Question

Calculate the molarity of pure water,
Density of pure water is 1 g ml¯1

Answer 1

Molarity is no of moles per litre.1g/ml density means that 1L (=1000 ml) weighs 1000g.

Mol wt of water is 18 g/mol

No of moles of water =1000/18 = 55.55 mol

So one litre of water has 55.55 mol water, and so molarity if water is 55.55 molar.

Answer 2

Density=mass/ volume
Thus mass =1/1=1
Molarity= no of moles/volume in L
No of moles=1/18=0.05
Molarity=0.05