Answer:
x = 2.2*10^23 molecules of H2O
Explanation:
H = 1g
O = 16g
H2O = 1g*2 + 16g
H2O = 18g = 1 mol of H2O
18 g___1 mol of H2O
6.38g__ x = 0.354 mol of H2O
1 mol______6.22*10^23 molecules
0.354 mol__x = 2.2*10^23 molecules of H2O