Question

How many molecules of H2O are there in 1.0 g of H2O?

Answer 1

Molar mass H₂O = 18.0 g/mol

number of moles :

1.0 / 18.0 => 0.055 moles

1 mole -------------- 6.02 x 10²³ molecules
0.055 moles --------  ? molecules

molecules = 0.055 x ( 6.02 x 10²³) / 1

molecules = 3.311x10²² / 1

= 3.311 x 10²² molecules

hope this helps!