Stoichiometry Chapter 9 Assignment & Problem Set

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1 Stoichiometry Name Warm-Ups (Show your work for credit) Date 1. Date 2. Date 3. Date 4. Date 5. Date 6. Date 7. Date 8.

2 Stoichiometry 2 Study Guide: Things You Must Know Vocabulary (know the definition and what it means): conserve stoichiometry stoichiometric ratio Honors limiting reagent Honors excess reagent Honors: theoretical yield Honors: actual yield Honors: percent yield Learning Objectives: know how to interpret a balanced chemical equation in terms of atoms, molecules, moles, mass, and volume (gases). atoms and mass are conserved in a balanced chemical equation. how to perform mole-mole stoichiometric calculations. how to perform stoichiometric calculations starting with either particles, mass, or volume (gas) of one substance and ending with particles, mass, or volume (gas) of a different substance. Honors: how to determine limiting reagent and excess reagent in a chemical reaction, given the amount of each reactant. Honors: how to calculate percent yield from theoretical yield and actual yield.

3 Stoichiometry 3 Read Chapter 9: Stoichiometry (Regents can skip all of section 9.3) Lab 8: Quantitative Analysis Regents Tables : Table T : Important Formulas and Equations Warm-ups and problems will be collected before you take the test. Answer all problems in the space provided. For problems involving an equation, carry out the following steps: 1. Write the equation. 2. Substitute numbers and units. 3. Show the final answer with units. There is no credit without showing work. Mole-Mole Stoichiometric Calculations 1. Interpret the following equation in terms of relative numbers of representative particles (label each correctly) and numbers of moles reactants and products. 2K(s) + 2H 2O(l) 2KOH(aq) + H 2(g) 2. Interpret the following equation in terms of interacting numbers of moles of reactants and products. 4NH 3(g) + 6NO(g) 5N 2(g) + 6H 2O(g) 3. Regents only Tin(II) fluoride, formerly found in many types of toothpaste, is formed by the reaction Sn(s) + 2HF(g) SnF 2(s) + H 2(g) a. How many moles of SnF 2 can be made by reacting 12.3 moles of HF with tin? b. How many moles of hydrogen gas at STP are produced by reacting 0.92 moles of tin with HF? c. How many moles of HF are needed to produce 3.2 moles of H 2? 4. Carbon disulfide is an important industrial solvent. It is prepared by the reaction of coke with sulfur dioxide. 5C(s) + 2SO 2(g) CS 2(l) + 4CO(g) a. How many moles of CS 2 form when 2.7 mol C reacts? b. How many moles of carbon are needed to react with 5.44 mol SO 2? c. How many moles of carbon monoxide form at the same time that mol CS 2 forms?

4 Stoichiometry 4 5. Isopropyl alcohol (C 3H 7OH) burns in air according to this equation: 2C 3H 7OH(l) + 9O 2(g) 6CO 2(g) + 8H 2O(g) a. Calculate the moles of oxygen needed to react with 3.40 mol C 3H 7OH. b. Find the moles of each product formed when 3.40 mol C 3H 7OH reacts with oxygen. General Stoichiometric Calculations 6. Methanol (CH 3OH) is used in the production of many chemicals. Methanol is made by reacting carbon monoxide and hydrogen at high temperature and pressure. CO(g) + 2H 2(g) CH 3OH(g) a. How many moles of each reactant are needed to produce 3.60 x 10 2 g CH 3OH. b. Calculate the number of grams of CO are needed to produce 4.00 mol CH 3OH. c. How many grams of hydrogen are necessary to react with 2.85 mol CO? 7. The combustion of acetylene gas is represented by this equation: 2C 2H 2(g) + 5O 2(g) 4CO 2(g) + 2H 2O(g) a. How many grams of CO 2 and grams of H 2O are produced when 52.0g C 2H 2 burns? b. How many grams of oxygen are required to burn 52.0g C 2H 2? c. Use the answers from a and b to show that this equation obeys the law of conservation of mass.

5 Stoichiometry 5 8. For the reaction: 2SO 2(g) + O 2(g) 2SO 3(g) a. How many grams of SO 3 can be made from 1.6 moles of SO 2? b. How many grams of SO 3 can be produced from 27 grams of O 2? c. How many grams of SO 3 can be made from 8.4 x molecules of O 2? d. How many liters, at STP, of O 2 are needed to produce 85.2 liters of SO 3? 9. Regents Only The equation for the combustion of carbon monoxide is 2CO(g) + O 2(g) 2CO 2(g) How many liters of oxygen are required to burn 3.86L of carbon monoxide? 10. Regents Only Lithium nitride reacts with water to form ammonia and aqueous lithium hydroxide. Li 3N(s) + 3H 2O(l) NH 3(g) + 3LiOH(aq) a. What mass of water is needed to react with 32.9g Li 3N? b. When reaction a takes place, how many molecules of NH 3 are produced? c. Calculate the number of grams of Li 3N that must be added to excess water to produce 15.0L NH 3 (at STP). Limiting Reagent & Reaction Yield 11. Honors For each balanced equation, identify the limiting reagent for the given combination of reactants. a. 2H 2 + O 2 2H 2O 6.4 mol 3.4 mol b. 2P 2O 5 + 6H 2O 4H 3PO mol 1.52 mol

6 Stoichiometry Honors If 2.7 mol of C 2H 4 is reacted with 6.30 mol O 2 according to the equation for the complete combustion of ethene (C 2H 4): C 2H 4(g) + 3O 2(g) 2CO 2(g) + 2H 2O(g) a. Identify the limiting reagent. b. Calculate the moles of water produced. 13. Honors How many grams of SO 3 are produced when 20.0g FeS 2 reacts with 16.0g O 2 according to this balanced equation? 4FeS 2(s) + 15O 2(g) 2Fe 2O 3(s) + 8SO 3(g) 14. Honors Hydrazine (N 2H 4) is used as rocket fuel. It reacts with oxygen to form nitrogen and water. N 2H 4(l) + O 2(g) N 2(g) + 2H 2O(g) a. How many liters of N 2 (at STP) form when 1.0kg N 2H 4 reacts with 1.0kg O 2? b. How many grams of the excess reagent remain after the reaction? Reaction Yield 15. Honors What is the difference between an actual yield and a theoretical yield? Which yield is larger for a given reaction? How are these values used to determine percent yield?

7 Stoichiometry Honors Heating an ore of antimony (Sb 2S 3) in the presence of iron gives the element antimony and iron(ii) sulfide. Sb 2S 3(s) + 3Fe(s) 2Sb(s) + 3FeS(s) When 15.0g Sb 2S 3 reacts with an excess of Fe, 9.84g Sb is produced. What is the percent yield of this reaction? 17. Honors For the reaction: 2SO 2(g) + O 2(g) 2SO 3(g) a. How many liters of SO 3 can be prepared starting with 32 g of SO 2 and 1.2 x molecules of O 2? Which reagent is limiting? b. How much of the excess reagent will be left after the reaction? c. For the reaction above, 125 g of SO 3 are produced by reacting 128 g of SO 2 with 39 g of O 2. What is the percent yield of the reaction? 18. Honors If the reaction below proceeds with a 96.8% yield, how many kilograms of CaSO4 are formed when 5.24 kg SO 2 reacts with an excess of CaCO 3and O 2? 2CaCO 3(s) + 2SO 2(g) + O 2(g) 2CaSO 4(s) + 2CO 2(g)

8 Stoichiometry Honors The white limestone cliffs of Dover, England, contain a large percentage of calcium carbonate (CaCO 3). A sample of limestone weighing 84.4g reacts with an excess of hydrochloric acid to form calcium chloride. CaCO 3 + 2HCl CaCl 2 + H 2O + CO 2 The mass of calcium chloride formed is 81.8g. What is the percentage of calcium carbonate in the limestone? Review 20. Write a balanced chemical equation for each reaction: a. The complete combustion of isopropyl alcohol (C 3H 7OH) produces carbon dioxide and water vapor. b. When a mixture of aluminum and iron(ii) oxide is heated, metallic iron and aluminum oxide are produced. 21. Write the formula for each compound. a. aluminum carbonate b. silicon dioxide c. potassium sulfide d. manganese(ii) chromate e. sodium bromide 22. What is the molecular formula of oxalic acid, molar mass 90g/mol? Its percent composition is 26.7% C, 2.2%H, and 71.1% O. 23. Write a net ionic equation for each of the following: a. Ba(NO 3) 2(aq) + Na 2SO 4(aq) BaSO 4(s) + NaNO 3(aq) b. H 2SO 4(aq) + Mg(OH) 2(aq) MgSO 4(aq) + H 2O(l)