Multiple Choice
Identify the species that is being oxidized in the following balanced reaction.
3 Pb2+ (aq) + 2 Cr (s) → 3 Pb (s) + 2 Cr3+ (aq)
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20. Electrochemistry
Standard Reduction Potentials
Multiple Choice
Rank the given metal ions in order of increasing strength as an oxidizing agent.
Pb2+ (-0.13 V), Mn2+ (-1.18 V), Cu2+ (+0.16 V), Co3+ (+1.82 V), Fe3+ (+0.77 V)
A
Pb2+ < Cu2+ < Mn2+ < Co3+ < Fe3+
B
Co3+ < Fe3+ < Cu2+ < Pb2+ < Mn2+
C
Mn2+ < Pb2+ < Cu2+ < Fe3+ < Co3+
D
Mn2+ < Pb2+ < Cu2+ < Co3+ < Fe3+
Verified step by step guidance1
Identify that the strength of an oxidizing agent is related to its standard reduction potential (E°). A higher (more positive) E° value means a stronger oxidizing agent because it more readily gains electrons (is reduced).
List the given metal ions along with their standard reduction potentials: Pb^{2+} (-0.13 V), Mn^{2+} (-1.18 V), Cu^{2+} (+0.16 V), Co^{3+} (+1.82 V), Fe^{3+} (+0.77 V).
Rank the ions in order of increasing strength as oxidizing agents by arranging them from the lowest to the highest standard reduction potential: start with the most negative E° and move to the most positive E°.
Write the order explicitly as: Mn^{2+} < Pb^{2+} < Cu^{2+} < Fe^{3+} < Co^{3+}, since Mn^{2+} has the lowest E° and Co^{3+} has the highest E°.
Confirm that this ranking matches the concept that ions with higher positive E° values are stronger oxidizing agents, and those with lower or negative E° values are weaker oxidizing agents.
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