Name______________________________________ Practice Problems: Limiting and Excess Reactants and Percent Yield Use a separate sheet of paper for your calculations. Write the answers on this sheet and attach your calculations to this sheet before turning in your work. 1. Calcium hydroxide, used to neutralize acid spills, reacts with hydrochloric acid according to the following equation: ___Ca(OH)2 + ___HCl ___CaCl2 + ___H2O a. If you have spilled 6.3 mol of HCl and put 2.8 mol of Ca(OH)2 on it, which substance is the limiting reactant? b. How many moles of the excess reactant remain? 2. Aluminum oxidizes according to the following equation: ___Al + ___O2 ___Al2O3 a. Powdered Al (0.048 mol) is placed into a container containing 0.030 mol O2. What is limiting reactant? b. How many moles of the excess reactant remain? 3. Heating zinc sulfide in the presence of oxygen yields the following: ___ZnS + ___O2 ___ZnO + ___SO2 a. If 1.72 mol of ZnS is heated in the presence of 3.04 mol of O2, which is the limiting reactant? (Balance the equation first) b. How many moles of the excess reactant remain? 4. Chlorine can replace bromine in bromide compounds forming a chloride compound and elemental bromine. The following equation is an example of the reaction: ___KBr(aq) + ___Cl2(aq) ___KCl(aq) + ___Br2(l) a. When 0.855g of Cl2 and 3.205g of KBr are mixed in solution, which is the limiting reactant? b. How many grams of each product are formed? 5. A process by which zirconium metal can be produced from the mineral zirconium (IV) orthosilicate, ZrSiO4, starts by reacting it with chlorine gas to form zirconium (IV) chloride. ___ZrSiO4 + ___Cl2 ___ZrCl4 +___SiO2 + ___O2 What mass of ZrCl4 can be produced if 862g of ZrSiO4 and 950.g of Cl2 are available? (You must first determine limiting reactant). 6. In the reaction BaCO3 + 2HNO3 Ba(NO3)2 + CO2 + H2O, what mass of Ba(NO3)2 can be formed by combining 55g BaCO3 and 26g HNO3? 7. Huge quantities of sulfur dioxide are produced from zinc sulfide by means of the following reaction. 2 ZnS(s) + 3 O2(g) 2 ZnO(s) + 2 SO2(g) If the typical yield is 86.78%, how much SO2 should be expected if 4897g of ZnS are used? 8. Aspirin, C9H8O4, is synthesized by the reaction of salicylic acid, C7H6O3, with acetic anhydride, C4H6O3. 2 C7H6O3 + C4H6O3 2 C9H8O4 + H2O a. When 20.0 g of C7H6O3and 20.0g of C4H6O3 react, which is the limiting reagent? b. What mass in grams of aspirin are formed? 9. Dichlorine monoxide, Cl2O is sometimes used as a powerful chlorinating agent in research. It can be produced by passing chlorine gas over heated mercury (II) oxide according to the following equation: ___HgO + ___Cl2 ___HgCl2 + ___Cl2O What is the percent yield, if the quantity of the reactants is sufficient to produce 0.86g of Cl2O but only 0.71 g is obtained? 10. In the commercial production of the element arsenic, arsenic(III) oxide is heated with carbon, which reduces the oxide to the metal according to the following equation: 2As2O3 + 3C 3CO2 + 4As a. If 8.87g of As2O3 is used in the reaction and 5.33 g of As is produced, what is the percent yield? b. If 67 g of carbon is used up in a different reaction and 425g of As is produced, calculate the percent yield of this reaction. 11. Assume that the following hypothetical reaction takes place. 2A + 7B 4C + 3D Calculate the percent yield in each of the following cases: a. The reaction of 0.0251 mol of A produces 0.0349 mol of C. b. The reaction of 1.19 mol of A produces 1.41 mol of D. c. The reaction of 189 mol of B produces 39 mol of D. d. The reaction of 3500 mol of B produces 1700 mol of C.