SiO2 (s) + 4 HF (g) → SiF4 (g) + 2 H2O (l) Sample Problem 9-6 Silicon dioxide (quartz) is usually quite unreactive, but reacts readily with hydrogen fluoride according to the following equation: SiO2 (s) + 4 HF (g) → SiF4 (g) + 2 H2O (l) If 2.0 mol of HF are exposed to 4.5 mol of SiO2, which is the limiting reagent?

N2H4 (l) + 2 H2O2 (l) → N2 (g) + 4 H2O (g) Practice Problem #1 Some rocket engines use a mixture of hydrazine, N2H4, and hydrogen peroxide, H2O2, as the propellant. The reaction is N2H4 (l) + 2 H2O2 (l) → N2 (g) + 4 H2O (g) Which is the limiting reactant in this reaction when 0.750 mol of hydrazine is mixed with 5.00 mol of H2O2? How much of the excess reactant, in moles, remains? How much of each product, in moles, is formed?

Practice Problem #2 If 20.5 g of chlorine is reacted with 20.5 g of sodium, which reactant is in excess? How do you know?

3 Fe (s) + 4 H2O (g) → Fe3O4 (s) + 4 H2 (g) Sample Problem 9-7 The black oxide of iron, Fe3O4, is the mineral magnetite. It can be made in the lab. 3 Fe (s) + 4 H2O (g) → Fe3O4 (s) + 4 H2 (g) When 36.0 g of steam is mixed with 167 g of Fe, which is the limiting reagent? What mass of iron oxide is produced? What mass of excess reagent remains when the reaction is completed?