n H2 = m H2 / Mr H2
n H2 = 2 / 2
n H2 = 1 mol
n O2 = m O2 / Mr O2
n O2 = 4 / 32
n O2 = 0.125 mol
O2 is a limiting reactant
n H2O = (coef. H2O / coef. O2) • n O2
n H2O = (2 / 1) • 0.125
n H2O = 0.25 mol
m H2O = n H2O • Mr H2O
m H2O = 0.25 • 18
m H2O = 4.5 gr
