Multiple Choice
What is the value (in V) of E°cell for the following reaction? Zn2+ (aq) + Pb (s) ⇌ Zn (s) + Pb2+ (aq)
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20. Electrochemistry
Standard Reduction Potentials
Multiple Choice
Which of the following statements correctly compares the standard reduction potentials (at 25°C) of Cu^{2+}/Cu and Cd^{2+}/Cd?
A
Cu^{2+}/Cu and Cd^{2+}/Cd have equal standard reduction potentials.
B
Both Cu^{2+}/Cu and Cd^{2+}/Cd have negative standard reduction potentials.
C
Cd^{2+}/Cd has a higher standard reduction potential than Cu^{2+}/Cu.
D
Cu^{2+}/Cu has a higher standard reduction potential than Cd^{2+}/Cd.
Verified step by step guidance1
Recall that the standard reduction potential (E°) measures the tendency of a species to gain electrons and be reduced under standard conditions (25°C, 1 M concentration, 1 atm pressure). A higher (more positive) E° means a stronger oxidizing agent and a greater tendency to be reduced.
Look up or recall the standard reduction potentials for the two half-reactions: for copper, the half-reaction is \(\mathrm{Cu^{2+} + 2e^- \rightarrow Cu}\), and for cadmium, it is \(\mathrm{Cd^{2+} + 2e^- \rightarrow Cd}\).
Compare the numerical values of the standard reduction potentials: copper typically has a positive or less negative E° value compared to cadmium, which usually has a more negative E° value, indicating copper ions are more easily reduced than cadmium ions.
Understand that because copper has a higher standard reduction potential, it means \(\mathrm{Cu^{2+}/Cu}\) is a stronger oxidizing agent and more likely to gain electrons than \(\mathrm{Cd^{2+}/Cd}\) under standard conditions.
Conclude that the correct statement is that \(\mathrm{Cu^{2+}/Cu}\) has a higher standard reduction potential than \(\mathrm{Cd^{2+}/Cd}\), which aligns with the given correct answer.
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