The standard reduction potentials at 25 deg C are: Zn²+(aq) + 2e⁻ - Zn(s), E* = -0.762 V Cr³+(aq) + 3e⁻ - Cr(s), E* = -0.740 V 2H^+(aq) + 2e⁻ - H2(g), E* = 0.00 V Fe³+(aq) + e⁻ - Fe²+(aq), E* = +0.77 V Which species is the strongest reducing agent?

Question

The standard reduction potentials at 25 deg C are: Zn²+(aq) + 2e⁻ -> Zn(s), E* = -0.762 V Cr³+(aq) + 3e⁻ -> Cr(s), E* = -0.740 V 2H^+(aq) + 2e⁻ -> H2(g), E* = 0.00 V Fe³+(aq) + e⁻ -> Fe²+(aq), E* = +0.77 V Which species is the strongest reducing agent?

Accepted Answer

Zn. A reducing agent is oxidized in a reaction. The species with the most negative standard reduction potential is most easily oxidized and hence is the strongest reducing agent. Among the given options: Zn has E* = -0.762 V (most negative), Cr has E* = -0.740 V, H2 has E* = 0.00 V, Fe²+ has E* = +0.77 V (already a reduced form but its reduction potential as given is for Fe³+/Fe²+). The most negative reduction potential belongs to Zn, making Zn the strongest reducing agent.

The standard reduction potentials at 25 deg C are: Zn²+(aq) + 2e⁻ -> Zn(s), E* = -0.762 V Cr³+(aq) + 3e⁻ -> Cr(s), E* = -0.740 V 2H^+(aq) + 2e⁻ -> H2(g), E* = 0.00 V Fe³+(aq) + e⁻ -> Fe²+(aq), E* = +0.77 V Which species is the strongest reducing agent?

Solution

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