Practice Problems Stoich!

Transcription

1 Practice Problems Stoich! Name: **YOUR ANSWERS MUST INCLUDE THE PROPER NUMBER OF SIG FIGS AND COMPLETE UNITS IN ORDER TO RECEIVE CREDIT FOR THE PROBLEM.** BALANCE THE FOLLOWING EQUATIONS TO USE IN QUESTIONS 5 14: 1. Al + O2 Al2O3 2. Cu + AgNO3 Ag + Cu(NO3)2 3. Zn + HCl ZnCl2 + H2 4. Fe + Cl2 FeCl3 PERFORM THE FOLLOWING STOICHIOMETRIC CALCULATIONS: 5. Zinc reacts with hydrochloric acid to produce zinc chloride and hydrogen. How many moles of HCl are required to produce 7.50 moles of ZnCl2? 6. Copper metal reacts with silver nitrate to form silver and copper(ii) nitrate. How many grams of copper are required to form 250 g of silver? 7. When aluminum is burned in excess oxygen, aluminum oxide is produced. How many grams of oxygen are required to produce 0.75 moles of Al2O3? 8. How many grams of iron(iii) chloride are produced when 15.3 g of iron react with excess chlorine gas? 9. Copper metal reacts with silver nitrate to form silver and copper(ii) nitrate. How many moles of silver will be produced from 3.65 moles of silver nitrate? 10. The mole ratios for the equation A + B C + D are shown. Based on the mole ratios, write the balanced general chemical equation represented. Substances Mole Ratio Substances Mole Ratio A:B 2:3 B:C 3:1 A:C 2:1 B:D 1:2 A:D 1:3 C:D 1:6 11. Fill in the diagram with the conversion factors that would be used to determine the mass of Substance X required to form a certain mass of Substance Y. 15. Fill in the boxes with the appropriate number of molecules of Substance Y and Substance Z to show the decomposition of Substance X in the correct ratios.

2 16. A dimensional analysis setup to determine the mass of Fe that can be fully oxidized by 8.93 grams of O 2 is shown. Explain what is incorrect in this setup and how to fix the setup to make it correct. 18..Find the mole ratio of lead (II) nitrate to potassium nitrate in this chemical reaction. KI + Pb(NO 3) 2 PbI 2 + KNO How many moles of zinc chloride can be produced from 15.3 moles of HCl? Zn + HCl ZnCl 2 + H In this chemical reaction, 6 moles of each of the reactants is combined. Mg + N 2 Mg 3N 2 b) How many moles of magnesium nitride can be made? 24. What is stoichiometry? 25. What is a mole ratio? 26. Balance the following equation and determine the possible mole ratios. 27 List the four steps to solve stoichiometric problems. 30. In a reaction, g of sodium reacts with g of ferric oxide to form sodium oxide and iron metal. Calculate the mass of solid iron produced. 34 Balance this equation. Then, show that the Law of Conservation of Matter is being obeyed at the particle level, the mole level, and the mass level. Fe 2O 3 + C Fe + CO

3 35. Aluminum metal is burned in oxygen gas. a. Write the balanced equation for this reaction grams of sodium hydroxide is reacted with grams of magnesium nitrate, according to the reaction NaOH + Mg(NO 3) 2 NaNO 3 + Mg(OH) 2. a) Write the balanced chemical equation for this reaction.

4 SHORT ANSWER Stoichiometry Review Ch. 9 BALANCED EQUATIONS 1. 4 Al + 3 O2 2 Al2O3 2. Cu + 2 AgNO3 2 Ag + Cu(NO3)2 3. Zn + 2 HCl ZnCl2 + H Fe + 3 Cl2 2 FeCl3 STOICHIOMETRIC CALCULATIONS mol HCl g Cu g O g FeCl mol Ag 10 ANS: 2A + 3B C + 6D ANSWER KEY PTS: 1 DIF: Bloom's Level 3 NAT: UCP.2 B.1 B.3 11/47. ANS: A) molar mass of Substance X B) mole ratio between substance X and substance Y C) molar mass of substance Y PTS: 1 DIF: Bloom's Level 2 NAT: UCP.2 UCP.3 B.3 15/48. ANS: Six molecules of diatomic Substance Y, 4 molecules of Substance Z. PTS: 1 DIF: Bloom's Level 5 NAT: UCP.2 B.3

5 16/49.ANS: The mole ratio is reversed; it should be 4 moles of Fe/3 moles O2. This is because the number of moles of oxygen must be on the bottom of the fraction in order to cancel out the moles of oxygen in the previous fraction (molar mass of oxygen).. 18/51. ANS: 1:2 PTS: 1 DIF: Bloom's Level 3 NAT: B.3 24/57. ANS: Stoichiometry is a study of quantitative relationships between the amounts of reactants used and the products formed by a chemical reaction. PTS: 1 DIF: 1 REF: Page 354 OBJ: Identify the quantitative relationships in a balanced chemical equation. NAT: UCP.3 B.3 TOP: Identify the quantitative relationships in a balanced chemical equation. KEY: Stoichiometry MSC: 1 25/58. ANS: A mole ratio is the ratio between the numbers of moles of any two substances in a balanced chemical equation. PTS: 1 DIF: 1 REF: Page 356 OBJ: Determine the mole ratios from a balanced chemical equation. NAT: UCP.3 B.3 TOP: Determine the mole ratios from a balanced chemical equation. KEY: Mole ratio MSC: 1 26/59. ANS: The balanced chemical equation is: The possible mole ratios are: PTS: 1 DIF: 2 REF: Page 356 OBJ: Determine the mole ratios from a balanced chemical equation. NAT: UCP.3 B.3 TOP: Determine the mole ratios from a balanced chemical equation. KEY: Mole ratio MSC: 3

6 27/60.ANS: The four steps to solve stoichiometric problems are: a. Write a balanced chemical equation. b. Determine the moles of a given substance using a mass-to-mole conversion. c. Determine the moles of an unknown substance from the moles of the given substance. d. Determine the mass of an unknown substance from the moles of the unknown substance using a mole-to-mass conversion. PTS: 1 DIF: 1 REF: Page 363 OBJ: Explain the sequence of steps used in solving stoichiometric problems. NAT: UCP.1 UCP.3 B.3 TOP: Explain the sequence of steps used in solving stoichiometric problems. KEY: Using stoichiometry MSC: 2 PROBLEM 30/63. ANS: g PTS: 1 DIF: 3 REF: Page 367 OBJ: Calculate the mass of a product when the amounts of more than one reactant are given. NAT: UCP.3 B.3 TOP: Calculate the mass of a product when the amounts of more than one reactant are given. KEY: Product mass calculation MSC: 3 NOT: First, calculate the actual ratio. Then, convert the number of moles of ferric oxide to the number of moles of iron. ESSAY 34/67. ANS: Fe 2O 3 + 3C 2Fe + 3CO Particles: 2 atoms Fe, 3 atoms O, 3 atoms C as reactants; 2 atoms Fe, 3 atoms O, 3 atoms C as products Moles: 2 moles Fe, 3 moles O, 3 moles C as reactants; 2 moles Fe, 3 moles O, 3 moles Cas products Mass: 1( ) + 3(12.01) = 2 (55.847) + 3 (84.027); g = PTS: 1 DIF: Bloom's Level 6 NAT: UCP.2 B.3 35/68. ANS: a) 4Al(s) + 3O 2(g) 2Al 2O 3(s). PTS: 1 DIF: Bloom's Level 4 NAT: UCP.2 UCP.3 B.3 37/70. ANS: a) 2 NaOH + Mg(NO 3) 2 2 NaNO 3 + Mg(OH) 2.