Metallic magnesium reacts with steam to produce magnesium hydroxide and hydrogen gas. If 17.1 g of Mg are heated with 9 g of H2O, what is the limiting reactant? I know limiting reactant is H2O. How much of the excess reactant is left? Answer in units of mol How much Mg(OH)2 is formed? Answer in units of g How much H2 is formed? Answer in units of g.