ch18 - 18 18.1 2 Ag+(aq) + Ni(s) Electrochemistry 2 Ag(s) +...

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18 Electrochemistry 18.1 2 Ag + (aq) + Ni(s) 2 Ag(s) + Ni 2+ (aq) There is a Ni anode in an aqueous solution of Ni 2+ , and a Ag cathode in an aqueous solution of Ag + . A salt bridge connects the anode and cathode compartment. The electrodes are connected through an external circuit. 18.2 Fe(s) Fe 2+ (aq) Sn 2+ (aq) Sn(s) 18.3 Pb(s) + Br 2 (l) Pb 2+ (aq) + 2 Br(aq) There is a Pb anode in an aqueous solution of Pb 2+ . The cathode is a Pt wire that dips into a pool of liquid Br 2 and an aqueous solution that is saturated with Br 2 . A salt bridge connects the anode and cathode compartment. The electrodes are connected through an external circuit. 18.4 (a) and (b) (c) 2 Al(s) + 3 Co 2+ (aq) 2 Al 3+ (aq) + 3 Co(s) (d) Al(s) Al 3+ (aq) Co 2+ (aq) Co(s) 11
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18.5 Al(s) + Cr 3+ (aq) Al 3+ (aq) + Cr(s) ΔG o = nFE o = (3 mol e) V C 1 J 1 V) (0.92 e mol 1 C 96,500 _ = 266,340 J = 270 kJ 18.6 oxidation: Al(s) Al 3+ (aq) + 3 e E o = 1.66 V reduction: Cr 3+ (aq) + 3 e Cr(s) E o = ? overall Al(s) + Cr 3+ (aq) Al 3+ (aq) + Cr(s) E o = 0.92 V The standard reduction potential for the Cr 3+ /Cr half cell is: E o = 0.92 1.66 = 0.74 V 18.7 (a) Cl 2 (g) + 2 e 2 Cl(aq)E o = 1.36 V Ag + (aq) + e Ag(s) E o = 0.80 V Cl 2 has the greater tendency to be reduced (larger E o ). The species that has the greater tendency to be reduced is the stronger oxidizing agent. Cl 2 is the stronger oxidizing agent. (b) Fe 2+ (aq) + 2 e Fe(s) E o = 0.45 V Mg 2+ (aq) + 2 e Mg(s) E o = 2.37 V The second half-reaction has the lesser tendency to occur in the forward direction (more negative E o ) and the greater tendency to occur in the reverse direction. Therefore, Mg is the stronger reducing agent. 18.8 (a) 2 Fe 3+ (aq) + 2 I(aq) 2 Fe 2+ (aq) + I 2 (s) reduction: Fe 3+ (aq) + e Fe 2+ (aq) E o = 0.77 V oxidation: 2 I(aq) I 2 (s) + 2 e E o = 0.54 V overall E o = 0.23 V Because E o for the overall reaction is positive, this reaction can occur under standard- state conditions. (b) 3 Ni(s) + 2 Al 3+ (aq) 3 Ni 2+ (aq) + 2 Al(s) oxidation: Ni(s) Ni 2+ (aq) + 2 e E o = 0.26 V reduction: Al 3+ (aq) + 3 e Al(s) E o = 1.66 V overall E o = 1.40 V Because E o for the overall reaction is negative, this reaction cannot occur under standard-state conditions. This reaction can occur in the reverse direction. 18.9 (a) D is the strongest reducing agent. D + has the most negative standard reduction potential. A 3+ is the strongest oxidizing agent. It has the most positive standard reduction potential. (b) An oxidizing agent can oxidize any reducing agent that is below it in the table. B 2+ can oxidize C and D. A reducing agent can reduce any oxidizing agent that is above it in the table.
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This note was uploaded on 08/27/2008 for the course CHEM 1280 taught by Professor Schmidt during the Fall '07 term at Toledo.

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ch18 - 18 18.1 2 Ag+(aq) + Ni(s) Electrochemistry 2 Ag(s) +...

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