8 g of water contains 1 mol of water molecules.
or 18 g of water contains 6.022 x 1023 water molecules.
or 1 g of water contains (6.022 x 1023)/ 18 water molecules and the number comes out to be 3.3455 x 1022.
So the number of water molecules present in 1 g of water is 3.3455 x 1022.