Question

The standard reduction potentials at 298 K for the following half cell reactions are given below: $Z{{n}^{2+}}(aq)+2{{e}^{-}}\rightleftharpoons Zn(s)-0.762$ $C{{r}^{3+}}(aq)+3{{e}^{-}}\rightleftharpoons Cr(s)-0.74$ $2{{H}^{+}}(aq)+2{{e}^{-}}\rightleftharpoons {{H}_{2}}(g)\,0.00$ $F{{e}^{3+}}(aq)+{{e}^{-}}\rightleftharpoons F{{e}^{2+}}(aq)+0.77$ Which one of the following is the strongest reducing agent?

• A. $Zn(s)$
• B. $Cr(s)$
• C. ${{H}_{2}}(g)$
• D. $F{{e}^{2+}}(aq)$

Answer 1

Answer: (A)

$Zn(s)$

Answer 2

The metals having higher -ve value of standard reduction potential are placed above hydrogen in electrochemical series. The metals placed above hydrogen has a great tendency to donate electrons or oxidising power. The metals having great oxidising power are strongest reducing agent. Zinc has higher-ve value of standard reduction potential. Therefore, it is the strongest reducing agent.