Chem 162-2011 Chapter 18-Some Electrochemistry practice

Chem 162-2011 Chapter 18-Some Electrochemistry practice -...

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CHAPTER 18 ELECTROCHEMISTRY Problems to prepare students for Chem 162 hourly exam III. “ELECTROCHEMISTRY” covers Zumdahl chapter 17. OXIDATION-REDUCTION REACTION CONCEPTS OXIDATION-REDUCTION REACTION CALCULATIONS GALVANIC CELLS & REDUCTION-POTENTIAL CONCEPTS REDUCTION POTENTIAL CALCULATIONS FREE ENERGY, EQUILIBRIA AND CELL POTENTIAL CALCULATIONS/NERNST EQUATION ELECTROLYSIS ELECTRIC WORK/AMPERES BATTERIES AND CORROSION Chapter 17 practice problems 1
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OXIDATION-REDUCTION REACTION CONCEPTS 35 Chem 162-2007 Final exam + answers Chapter 18 - Electrochemistry Oxidation-reduction reaction concepts What is the coefficient of H + when the following skeletal reaction is balanced in acid with the lowest possible set of integer coefficients? IO 3 - (aq) + Tl + +Cl - ICl 2 - + Tl 3+ A. 2 B. 3 C. 4 D. 5 E . 6 +5 -2 +1 -1 +1 -1 +3 IO 3 - (aq) + Tl + + Cl - ICl 2 - + Tl 3+ IO 3 - + Cl - → ICl 2 - IO 3 - + 2Cl - → ICl 2 - IO 3 - + 2Cl - → ICl 2 - + 3H 2 O IO 3 - + 2Cl - + 6H + → ICl 2 - + 3H 2 O IO 3 - + 2Cl - + 6H + + 4e - → ICl 2 - + 3H 2 O Tl + → Tl 3+ Tl + → Tl 3+ + 2e - IO 3 - + 2Cl - + 6H + + 4e - → ICl 2 - + 3H 2 O 2(Tl + → Tl 3+ + 2e - ) IO 3 - + 2Cl - + 6H + + 2Tl + → ICl 2 - + 3H 2 O + 2Tl 3+ Chapter 17 practice problems 2
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Chem 162-2007 Exam III + Answers Chapter 18 – Electrochemistry Oxidation-reduction reaction concepts 3 Consider the following two half reactions and the statements that follow: Ag + (aq) + 1 e - Ag(s) 2 Ag + (aq) + 2 e - 2 Ag(s) X. Gº is the same for both reactions Y. Eº is the same for both reactions Z. Both reactions are oxidations Which of the above statements is (are) correct? A. X only B. X and Y only C. Y and Z only D .Y only E. Z only X. False. Gibbs free energy is an extensive property. Therefore, the value depends on the quantity. Since the second equation is double that of the first, the Gibbs free energy is double for the second reaction. Y. True. Voltage is an intensive property. Therefore, the value is unrelated to the quantity; i.e., doubling the equation doesn’t change the voltage. Hence, the voltage of the second reaction is the same as the voltage of the first reaction. Z. False. Both reactions are reductions. Chapter 17 practice problems 3
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Chem 162-2007 Exam III + Answers Chapter 18 – Electrochemistry Oxidation-reduction reaction concepts 4 When the following half reaction (shown unbalanced) occurs in acidic medium, the number of moles of electrons transferred per mole of Br 2 is Br 2 BrO 3 - (aq) A. 1 B. 2 C. 5 D. 8 E . 10 Br 2 BrO 3 - Br 2 2BrO 3 - Br 2 + 6H 2 O 2BrO 3 - Br 2 + 6H 2 O 2BrO 3 - + 12H + Br 2 + 6H 2 O 2BrO 3 - + 12H + + 10e - Chapter 17 practice problems 4
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Chem 162-2007 Exam III + Answers Chapter 18 – Electrochemistry Oxidation-reduction reaction concepts 15 The coefficients ("a" and "b") needed to balance the following equation are Cr 2 O 7 2- (aq) + a Br - (aq) + H + (aq) Cr 3+ (aq) + b H 2 O + Br 2 (l) A. a = 8, b = 4 B . a = 6, b = 7
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This document was uploaded on 11/02/2011 for the course GEN CHEM 162 at Rutgers.

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Chem 162-2011 Chapter 18-Some Electrochemistry practice -...

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