Given the list of reduction potentials, which of the following species is the strongest reducing agent?

Li⁺(aq)+ e^–  →Li (s) E^o_red = -3.04 V

Zn²⁺(aq) + 2 e^– → Zn (s) E^o_red = -0.76 V

Ag⁺(aq)  + e^– → Ag (s) E^o_red = 0.80 V

Ce⁴⁺(aq)  + e^– → Ce³⁺ (s) E^o_red = 1.44 V

A. Ce⁴⁺

B. Zn²⁺

C. Li

D. Ag

Explanation

This question is testing your understanding of the redox chemistry and reduction potentials. To answer this question, you must first know that a reducing agent is itself oxidized. Therefore, the strongest reducing agent is going to be the species that is most readily oxidized. The Nernst equation, DG = -nFE, shows that a spontaneous reaction (DG < 0) corresponds to an electrochemical potential, E, that is greater than zero.

Since Ce⁴⁺ is spontaneously reduced, choice A can be eliminated. Zn²⁺ is already in its oxidized form and therefore cannot be oxidized further making B the wrong answer. Considering answer choices C and D, you must reverse the reactions to find E^o_ox, which equals the negative of the reduction potential (E^o_ox = -E^o_red). Therefore, the oxidation of Ag(s) is a nonspontaneous reaction while the oxidation of Li(s) proceeds spontaneous with a potential of +3.04 V, making C the correct answer.

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