Question: how many molecules are in 1 ml of water?
Answer: Taking the density of water to be 1g/mL, 1000mL of water= 1000g water. =3.34*10^25 molecules of water. Or 3.34*10^23 molecules in 1ml. 18 g (molar mass) of H2O has ~6 x 10 to the power of 23 molecules.