Review. Reviewing Key Terms For each of the following terms, write a sentence that shows your understanding of its meaning. Knowledge/Understanding

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1 Review Reflecting on Chapter 10 Summarize this chapter in the format of your choice. Here are a few ideas to use as guidelines: Give two different definitions for the term oxidation. Give two different definitions for the term reduction. Define a half-. Give an example of an oxidation half- and a reduction half-. Compare the half- and oxidation number methods of balancing equations. Practise balancing equations using both methods. Write an example of a balanced chemical equation for a redox. Assign oxidation numbers to each element in the equation, then explain how you know it is a redox. Reviewing Key Terms For each of the following terms, write a sentence that shows your understanding of its meaning. ore oxidation reduction oxidation-reduction redox oxidizing agent reducing agent half- disproportionation oxidation numbers Knowledge/Understanding 1. For each below, write a balanced chemical equation by inspection. (a) zinc metal with aqueous silver nitrate (b) aqueous cobalt(ii) bromide with aluminum metal (c) metallic cadmium with aqueous tin(ii) chloride 2. For each in question 1, write the total ionic and net ionic equations. 3. For each in question 1, identify the oxidizing agent and reducing agent. 4. For each in question 1, write the two half-s. 5. When a metallic element reacts with a non-metallic element, which reactant is (a) oxidized? (b) reduced? (c) the oxidizing agent? (d) the reducing agent? 6. Use a Lewis structure to assign an oxidation number to each element in the following compounds. (a) BaCl 2 (b) CS 2 (c) XeF 4 7. Determine the oxidation number of each element present in the following substances. (a) BaH 2 (b) Al 4 C 3 (c) KCN (d) LiNO 2 (e) (NH 4 ) 2 C 2 O 4 (f) S 8 3 (g) AsO 3 + (h) VO 2 (i) XeO 3 F 2 (j) S 4 O 6 8. Identify a polyatomic ion in which chlorine has an oxidation number of Determine which of the following balanced chemical equations represent redox s. For each redox, identify the oxidizing agent and the reducing agent. (a) 2C 6 H O 2 12CO 2 + 6H 2 O (b) CaO + SO 2 CaSO 3 (c) H 2 + I 2 2HI (d) KMnO 4 + 5CuCl + 8HCl KCl + MnCl 2 + 5CuCl 2 + 4H 2 O 10. Determine which of the following balanced net ionic equations represent redox s. For each redox, identify the reactant that undergoes oxidation and the reactant that undergoes reduction. (a) 2Ag + (aq) + Cu (s) 2Ag (s) + Cu 2+ (aq) (b) Pb 2+ (aq) + S 2 (aq) PbS (s) (c) 2Mn BiO H + 2MnO 4 + 5Bi H 2 O Chapter 10 Oxidation-Reduction Reactions MHR 499

2 11. (a) Examples of molecules and ions composed only of vanadium and oxygen are listed below. In this list, identify molecules and ions in which the oxidation number of vanadium is the same. V 2 O 5 V 2 O 3 VO 2 VO VO 2 + VO 2+ VO 3 VO 4 3 V 3 O 9 3 (b) Is the following a redox? 2NH 4 VO 3 V 2 O 5 + 2NH 3 + H 2 O 12. The method used to manufacture nitric acid involves the following three steps. Step 1 4NH 3(g) + 5O 2(g) 4NO (g) + 6H 2 O (g) Step 2 2NO (g) + O 2(g) 2NO 2(g) Step 3 3NO 2(g) + H 2 O (l) 2HNO 3(aq) + NO (g) (a) Which of these steps are redox s? (b) Identify the oxidizing agent and the reducing agent in each redox. 13. In a synthesis involving elements A and B, the oxidation number of element A increases. What happens to the oxidation number of element B? How do you know? 14. Balance each of the following half-s. (a) The reduction of iodine to iodide ions (b) The oxidation of lead to lead(iv) ions (c) The reduction of tetrachlorogold(iii) ions, AuCl 4, to chloride ions and metallic gold (d) C 2 H 5 OH CH 3 COOH (acidic (e) S 8 H 2 S (acidic (f) AsO 2 AsO 3 4 (basic 15. Use the half- method to balance each of the following equations. (a) MnO 2 + Cl Mn 2+ + Cl 2 (acidic (b) NO + Sn NH 2 OH + Sn 2+ (acidic (c) Cd 2+ + V 2+ Cd + VO 3 (acidic (d) Cr Cr(OH) 4 + H 2 (basic (e) S 2 O NiO 2 Ni(OH) 2 + SO 3 2 (basic (f) Sn 2+ + O 2 Sn 4+ (basic 16. Use the oxidation number method to balance each of the following equations. (a) SiCl 4 + Al Si + AlCl 3 (b) PH 3 + O 2 P 4 O 10 + H 2 O (c) I 2 O 5 + CO I 2 + CO 2 (d) SO O 2 SO Complete and balance a net ionic equation for each of the following disproportionation s. (a) NO 2 NO 2 + NO 3 (acidic, which is one of the s involved in acid rain formation (b) Cl 2 ClO + Cl (basic, which is one of the s involved in the bleaching action of chlorine in basic solution 18. Balance each of the following net ionic equations. Then include the named spectator ions to write a balanced chemical equation. Include the states. (a) Co 3+ + Cd Co 2+ + Cd 2+ (spectator ions NO 3 ) (b) Ag + + SO 2 Ag + SO 2 4 (acidic conditions; spectator ions NO 3 ) (c) Al + CrO 2 4 Al(OH) 3 + Cr(OH) 3 (basic conditions; spectator ions Na + ) 19. If possible, give an example for each. (a) a synthesis that is a redox (b) a synthesis that is not a redox (c) a decomposition that is a redox (d) a decomposition that is not a redox (e) a double displacement that is a redox (f) a double displacement that is not a redox 20. Give an example of a in which sulfur behaves as (a) an oxidizing agent (b) a reducing agent 21. Write a balanced equation for a synthesis in which elemental oxygen acts as a reducing agent. 500 MHR Unit 5 Electrochemistry

3 22. Phosphorus, P 4(s), reacts with hot water to form phosphine, PH 3(g), and phosphoric acid. (a) Write a balanced chemical equation for this. (b) Is the phosphorus oxidized or reduced? Explain your answer. 23. The thermite, which is highly exothermic, can be used to weld metals. In the thermite, aluminum reacts with iron(iii) oxide to form iron and aluminum oxide. The temperature becomes so high that the iron is formed as a liquid. (a) Write a balanced chemical equation for the. (b) Is the a redox? If so, identify the oxidizing agent and the reducing agent. Inquiry 24. Iodine reacts with concentrated nitric acid to form iodic acid, gaseous nitrogen dioxide, and water. (a) Write the balanced chemical equation. (b) Calculate the mass of iodine needed to produce 28.0 L of nitrogen dioxide at STP. 25. Describe a laboratory investigation you could perform to decide whether tin or nickel is the better reducing agent. Include in your description all the materials and equipment you would need, and the procedure you would follow. 26. The following table shows the average composition, by volume, of the air we inhale and exhale, as part of a biochemical process called respiration. (The values are rounded.) Gas Oxygen Carbon dioxide Nitrogen and other gases Inhaled Air (% by volume) Exhaled Air (% by volume) How do the data indicate that at least one redox is involved in respiration? 27. Highly toxic phosphine gas, PH 3, is used in industry to produce flame retardants. One way to make phosphine on a large scale is by heating elemental phosphorus with a strong base. (a) Balance the following net ionic equation for the under basic conditions. P 4 H 2 PO 2 + PH 3 (b) Show that the in part (a) is a disproportionation. (c) Calculate the mass of phosphine that can theoretically be made from 10.0 kg of phosphorus by this method. Communication 28. Explain why, in a redox, the reducing agent undergoes oxidation. 29. Explain why you would not expect sulfide ions to act as an oxidizing agent. 30. Why can t the oxidation number of an element in a compound be greater than the number of valence electrons in one atom of that element? 31. Explain why the historical use of the word reduction, that is, the production of a metal from its ore, is consistent with the modern definitions of reduction. 32. Organic chemists sometimes describe redox s in terms of the loss or gain of pairs of hydrogen atoms. Examples include the addition of hydrogen to ethene to form ethane, and the elimination of hydrogen from ethanol to form ethanal. (a) Write a balanced equation for each. (b) Determine whether the organic reactant is oxidized or reduced in each. (c) Write a definition of oxidation and a definition of reduction based on an organic reactant losing or gaining hydrogen. (d) Would your definitions be valid for the synthesis and decomposition of a metal hydride? Explain your answer. Chapter 10 Oxidation-Reduction Reactions MHR 501

4 Making Connections 33. The compound NaAl(OH) 2 CO 3 is a component of some common stomach acid remedies. (a) Determine the oxidation number of each element in the compound. (b) Predict the products of the of the compound with stomach acid (hydrochloric acid), and write a balanced chemical equation for the. (c) Were the oxidation numbers from part (a) useful in part (b)? Explain your answer. (d) What type of is this? (e) Check your medicine cabinet at home for stomach acid remedies. If possible, identify the active ingredient in each remedy. 34. Two of the substances on the head of a safety match are potassium chlorate and sulfur. When the match is struck, the potassium chlorate decomposes to give potassium chloride and oxygen. The sulfur then burns in the oxygen and ignites the wood of the match. (a) Write balanced chemical equations for the decomposition of potassium chlorate and for the burning of sulfur in oxygen. (b) Identify the oxidizing agent and the reducing agent in each in part (a). (c) Does any element in potassium chlorate undergo disproportionation in the? Explain your answer. (d) Research the history of the safety match to determine when it was invented, why it was invented, and what it replaced. 35. Ammonium ions, from fertilizers or animal waste, are oxidized by atmospheric oxygen. The results in the acidification of soil on farms and the pollution of ground water with nitrate ions. (a) Write a balanced net ionic equation for this. (b) Why do farmers use fertilizers? What alternative farming methods have you heard of? Which farming method(s) do you support, and why? 36. One of the most important discoveries in the history of the chemical industry in Ontario was accidental. Thomas Carbide Willson ( ) was trying to make the element calcium from lime, CaO, by heating the lime with coal tar. Instead, he made the compound calcium carbide, CaC 2. This compound reacts with water to form a precipitate of calcium hydroxide and gaseous ethyne (acetylene). Willson s discovery led to the large-scale use of ethyne in numerous applications. (a) Was Willson trying to perform a redox? How do you know? Why do you not need to know the substances in coal tar to answer this question? (b) Write a balanced chemical equation for the of calcium carbide with water. Is this a redox? (c) An early use of Willson s discovery was in car headlights. Inside a headlight, the of calcium carbide and water produced ethyne, which was burned to produce light and heat. Write a balanced chemical equation for the complete combustion of ethyne. Is this a redox? (d) Research the impact of Willson s discovery on society, from his lifetime to the present day. Answers to Practice Problems and Short Answers to Section Review Questions Practice Problems: 1. Zn (s) + Fe 2+ (aq) Zn 2+ (aq) + Fe (s) 2.(a) 3Mg (s) + 2Al 3+ (aq) 3Mg 2+ (aq) + 2Al (s) (b) 2Ag + (aq) + Cd (s) 2Ag (s) + Cd 2+ (aq) 3.(a) Mg oxidized, Al 3+ reduced (b) Cd oxidized, Ag + reduced 4.(a) Al 3+ oxidizing agent, Mg reducing agent (b) Ag + oxidizing agent, Cd reducing agent 5. Al (s) Al 3+ (aq) + 3e, Fe 3+ (aq) + 3e Fe (s) 6.(a) Fe (s) Fe 2+ (aq) + 2e, Cu 2+ (aq) + 2e Cu (s) (b) Cd (s) Cd 2+ (aq) + 2e, Ag + (aq) + 1e Ag (s) 7.(a) Sn (s) Sn 2+ (aq) + 2e, Pb 2+ (aq) + 2e Pb (s) (b) Ag (s) Ag + + e, Au 3+ (aq) + 3e Au (s) (c) Zn (s) Zn 2+ (aq) + 2e, Fe 3+ (aq) + 3e Fe (s) 8. Hg 2 2+ (aq) Hg (l) + Hg 2+ (aq), Hg 2 2+ (aq) + 2e 2Hg (l), Hg 2 2+ (aq) 2Hg 2+ (aq) + 2e 9.(a) +3 (b) 0 (c) +6 (d) +5 (e) 0 (f) MHR Unit 5 Electrochemistry

5 10.(a) H, +1; S, +4; O, 2 (b) H, +1; O, 2 (c) H, +1; P, +5; O, 2 11.(a) +2 (b) 1 12.(a) Al, +3; H, +1; C, +4; O, 2 (b) N, 3; H, +1; P, +5; O, 2 (c) K, +1; H, +1; I, +7; O, 2 13.(a) yes (b) no 14.(a) H 2 O 2 oxidizing agent, Fe 2+ reducing agent 15. ClO 2 oxidized, Br 2 reduced 16. yes 17. Ce 4+ + e Ce Br Br 2 + 2e 19.(a) O 2 + 2H + + 2e H 2 O 2 (b) 2H 2 O O 2 + 4H + + 4e (c) 2NO H e N 2 + 6H 2 O 20.(a) ClO 3 + 6H + + 6e Cl + 3H 2 O (b) NO + 2H 2 O NO 3 + 4H + + 3e (c) Cr 2 O H + + 6e 2Cr H 2 O 21. Cr 2+ Cr 3+ + e 22. O 2 + 4e 2O 2 23.(a) Al + 4OH Al(OH) 4 + 3e (b) CN + 2OH CNO + H 2 O + 2e (c) MnO 4 + 2H 2 O + 3e MnO 2 + 4OH (d) CrO H 2 O + 3e Cr(OH) 3 + 5OH (e) 2CO H 2 O + 2e C 2 O OH 24.(a) FeO H + + 3e Fe H 2 O (b) ClO 2 + 2H 2 O + 4e Cl + 4OH 25.(a) 2Na + F 2 2NaF ox: Na Na + + e red: F 2 + 2e 2F (b) 3Mg + N 2 Mg 3 N 2 ox: Mg Mg e red: N 2 + 6e 2N 3 (c) 2HgO 2Hg + O 2 ox: 2O 2 O 2 + 4e red: Hg e Hg 26. 2Cu I 2CuI + I 3 27.(a) MnO 4 + 5Ag + 8H + Mn Ag + + 4H 2 O oxidizing agent, MnO 4 ; reducing agent, Ag (b) Hg + 2NO 3 + 4Cl + 4H + HgCl NO 2 + 2H 2 O oxidizing agent, NO 3 ; reducing agent, Hg (c) AsH 3 + 4Zn H 2 O H 3 AsO 4 + 4Zn + 8H + oxidizing agent, Zn 2+ ; reducing agent, AsH 3 (d) 3I 3 + 3H 2 O 8I + IO 3 + 6H + oxidizing agent, I 3 ; reducing agent, I 3 28.(a) 3CN + 2MnO 4 + H 2 O 3CNO + 2MnO 2 + 2OH oxidizing agent, MnO 4 ; reducing agent, CN (b) H 2 O 2 + 2ClO 2 + 2OH 2ClO 2 + O 2 + 2H 2 O oxidizing agent, ClO 2 ; reducing agent, H 2 O 2 (c) 6ClO + 2CrO 2 + 2H 2 O 3Cl 2 + 2CrO OH oxidizing agent, ClO ; reducing agent, CrO 2 (d) 2Al + NO 2 + H 2 O + OH NH 3 + 2AlO 2 oxidizing agent, NO 2 ; reducing agent, Al 29. CS 2 + 3O 2 CO 2 + 2SO 2 30.(a) B 2 O 3 + 6Mg 3MgO + Mg 3 B 2 (b) 8H 2 S + 8H 2 O 2 S H 2 O 31.(a) Cr 2 O Fe H + 2Cr Fe H 2 O (b) I NO 3 + 8H + 2IO NO 2 + 4H 2 O (c) 2PbSO 4 + 2H 2 O Pb + PbO 2 + 2SO H + 32.(a) 3Cl + 2CrO H 2 O 3ClO + 2CrO 2 + 2OH (b) 3Ni + 2MnO 4 + H 2 O 3NiO + 2MnO 2 + 2OH (c) I + 6Ce OH IO 3 + 6Ce H 2 O Section Review 10.1: 1.(a) yes; 2AgNO 3(aq) + Cd (s) 2Ag (s) + Cd(NO 3 ) 2(aq) ; 2Ag + (aq) + Cd (s) 2Ag (s) + Cd 2+ (aq); Ag + (aq) + e Ag (s) ; Cd (s) Cd 2+ (aq) + 2e (b) no (c) yes; 2Al (s) + 3HgCl 2(aq) 2AlCl 3(aq) + 3Hg (l) ; 2Al (s) + 3Hg 2+ (aq) 2Al 3+ (aq) + 3Hg (l) ; Al (s) Al 3+ (aq) + 3e ; Hg 2+ (aq) + 2e Hg (l) 2.(a) right side (b) left side 4. reducing agent 6.(a) K + + Na (l) Na + + K (l) (b) oxidizing agent, K + ; reducing agent, Na (l) 10.2: 2.(a) yes (b) no (c) no (d) yes 6.(a) +2 (b) +5 and 1 7.(a) N 2 + 3H 2 2NH 3 (0, 0, 3, +1); N 2 is oxidizing agent, H 2 is reducing agent (b) no 8.(a) 2C + O 2 2CO, Fe 2 O 3 + 3CO 2Fe + 3CO 2 (b) carbon reducing agent, oxygen oxidizing agent; carbon monoxide reducing agent, iron(iii) oxide oxidizing agent 10.3: 1.(a) 2C + 2e C 2 2, reduction (b) 2S 2 O 3 2 S 4 O e, oxidation (c) 4AsO H + + 8e As 4 O H 2 O, reduction (d) Br OH 2BrO 3 + 6H 2 O + 10e, oxidation 2.(a) 3Co 3+ + Au 3Co 2+ + Au 3+ (b) 3Cu + 2NO 3 + 8H + 3Cu NO + 4H 2 O (c) 3NO 3 + 8Al + 5OH + 2H 2 O 3NH 3 + 8AlO Ag + + HCHO + H 2 O 2Ag + HCOOH + 2H + 4.(b) 2NH 3 + 8OH N 2 O + 7H 2 O + 8e 5.(a) 2N 2 H 4 + N 2 O 4 3N 2 + 4H 2 O (b) N 2 O 4 is oxidizing agent, N 2 H 4 is reducing agent (c) 2NH 3 + ClO N 2 H 4 + Cl + H 2 O 6.(a) Larissa was right (b) 3Zn + SO H + 3Zn 2+ + S + 4H 2 O 10.4: 1. no, not a redox 2.(a) CH 3 COOH + 2O 2 2CO 2 + 2H 2 O (b) O 2 + 2H 2 SO 3 2HSO 4 + 2H + 3.(a) 8NH 3 + 3Cl 2 6NH 4 Cl + N 2 (b) 3Mn 3 O 4 + 8Al 4Al 2 O 3 + 9Mn Chapter 10 Oxidation-Reduction Reactions MHR 503