Question

The standard potentials at 298 K for the following half reactions are as given

Zn²⁺ + 2e $\rightleftarrows$ Zn Eŗ = –0.762 V

2H⁺ + 2e ® H₂ (g) Eŗ = 0.000 V

Cr³⁺ + 3e$\rightleftarrows$ Cr Eŗ = – 0.740 V

Fe³⁺ + 2e ® Fe²⁺ Eŗ = 0.772 V

Which of the following is the strongest reducing agent ?

• A. Zn (s)
• B. Cr
• C. H₂ (g)
• D. Fe²⁺ (aq)

Answer 1

Answer: (A)

Zn (s)

Answer 2

More negative the standard potential, least the reduction tendency of the ion. The corresponding atom has largest oxidation tendency and thus is a strong reducing agent. Zn is the strongest reducing agent.