stoichiometry

the math behind chemistry, well lets find out how many molecules there are in one gram of water:

Water has a molecular mass of 18, this means it weights 18 g per mole
One mole is 6.02 x 10 ^23 or 602,000,000,000,000,000,000,000
one mole of H2O= 18 g
1 g of water is 1/18 of a mole 3.34 x 10^22 so:
there are 33,400,000,000,000,000,000,000 molecules in one gram of H2O