The balanced reaction for the production of water from hydrogen and oxygen is: 2H₂ + O₂→ 2H₂O. Also, the relevant molar masses are the following:
Molar mass of H₂O = 18 g/mol
Molar mass of O₂ = 32 g/mol
We need not be concerned with the amount of hydrogen since we can derive the amount of oxygen that reacted based on the amount of product produced. The following equation is then set-up:
Mass of O₂ reacted =
202 g H2O x 1 mol
H2O/ 18 g H2O x 1 mol O2/ 2 mol H2O x 32 g O2/ 1 mol O2 = 179.56 g O2
Thus, we have determined that 179.56 g O2 reacted with H2 to produce 202 g of H2O.
