posted by megan .
how do you calculate the mass of water that will be produced when 5.0 grams of H2 is reacted with excess O2?
one O atom for every 2 H atoms
every H atom weighs 1 unit
every H2 molecule weighs 2 units
every O atom weighs 16 units
the sum of 2 units and 16 units is 18 units, the H2O mass
2/18 = Hydrogen mass / water mass = 1/9
(1/9) of our water mass is 5 grams
9*5 = 45 grams