posted by Karen .
Calculate the mass of water that will be produced when 5.0 grams of H2 is reacted with excess O2.
2H2 + O2 ==> 2H2O
mols H2 = grams/molar mass = ?
mols H2O produced = same as mols H2.(look at the coefficients in the balanced equation.)
g H2O = mols x molar mass