The alcohol in gasohol burns according to the reaction

C2H5OH(l) + 3O2(g) --> 2CO2(g) + 3H2O

how many grams of water are produced when 3.0 moles of C2H5OH are burned in an excess of oxygen gas?

1 answer

mols C2H5OH = 3.0
mols H2O produced = 3.0 mols EtOH x (3 mols H2O/1 mol EtOH) = 9 mols H2O produced.
g H2O = mols x molar mass.