Question

How many water molecules in a 0.90⋅g mass of water?

Answer 1

molecular mass of water = 18 gram

i.e 18 g of water contains 6.022×10^23 molecules

so by unitary method,

1 g water contains = (6.022×10^23)/18 molecules

hence, 0.9 g water will contain= (0.9×6.022×10^23)/18= 3.011×10^22 molecules