# CHhmwk7 - moore(jwm2685 – Homework 7 – vanden bout...

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Unformatted text preview: moore (jwm2685) – Homework 7 – vanden bout – (51640) 1 This print-out should have 29 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Using the set of smallest possible integer co- efficients to balance the redox equation ClO − 3 + I 2 → IO − 3 + Cl − (acidic solution), the coefficient for I 2 is 1. 3. correct 2. 1. 3. 2. 4. The correct coefficient is not given. 5. 4. Explanation: The oxidation number of Cl changes from +5 to- 1, so Cl is reduced. The oxidation number of I changes from 0 to +5, so I is oxidized. We set up oxidation and reduction half-reactions: Red: ClO − 3 → Cl − Oxid: I 2 → IO − 3 Cl atoms are balanced. We need 2 IO − 3 molecules to balance I: Oxid: I 2 → 2 IO − 3 Since this is an acidic solution, we use H 2 O and H + to balance O and H atoms, adding the H 2 O to the side needing oxygen: Red: 6 H + + ClO − 3 → Cl − + 3 H 2 O Oxid: 6 H 2 O + I 2 → 2 IO − 3 + 12 H + We balance the total charge in each half- reaction by adding electrons. In the preceding reduction reaction there is a total charge of +5 on the left and- 1 on the right. Six elec- trons are added to the left: Red: 6 e − + 6 H + + ClO − 3 → Cl − + 3 H 2 O Oxid: 6 H 2 O + I 2 → 2 IO − 3 + 12 H + + 10 e − The number of electrons gained by Cl must equal the number of electrons lost by I. We multiply the reduction reaction by 5 and the oxidation reaction by 3 to balance the elec- trons: Red: 30 e − + 30 H + + 5 ClO − 3 → 5 Cl − + 15 H 2 O Oxid: 18 H 2 O + 3 I 2 → 6 IO − 3 + 36 H + + 30 e − Adding the half-reactions gives 18 H 2 O + 3 I 2 + 30 H + + 5 ClO − 3 → 6 IO − 3 + 36 H + + 5 Cl − + 15 H 2 O Canceling like terms gives the overall bal- anced equation 3 H 2 O + 3 I 2 + 5 ClO − 3 → 6 IO − 3 + 6 H + + 5 Cl − 002 10.0 points How many electrons are required to balance the half reaction below? H + + ClO − + e −-→ Cl − + H 2 O 1. 3 2. 1 3. 2 correct 4. 4 Explanation: Each chlorine atom undergoes a change of oxidation state from +1 to- 1. This is there- fore a 2 electron process. 003 10.0 points Consider the reaction Zn(s) + OH − (aq) + H 2 O( ℓ ) + NO − 3 (aq) → Zn(OH) 2 − 4 (aq) + NH 3 (g) If the coefficient of NO − 3 in the balanced equation is 1, how many electrons are trans- ferred in the reaction? 1. 8 correct 2. 6 3. 2 4. 10 5. 4 Explanation: moore (jwm2685) – Homework 7 – vanden bout – (51640) 2 004 10.0 points In the reaction 2 MnO − 4 + 16 H + + 10 I − → 2 Mn 2+ + 8 H 2 O + 5 I 2 of permanganate anion with iodide in acidic solution, what has been reduced and what is the change in oxidation number?...
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## This note was uploaded on 05/02/2011 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas.

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CHhmwk7 - moore(jwm2685 – Homework 7 – vanden bout...

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