Q. The standard reduction potentials at 298 K for the following half reactions are given against each ${Zn}^{2 +}\ (aq)\ + \ {2e}^{-}\ \ \longrightarrow \ Zn\ (s);\ \ \ \ \ \ E^{{^\circ}}\ = \ - \ 0.762\ V$ ${Cr}^{3 +}\ (aq)\ + \ {3e}^{-}\ \ \longrightarrow \ Cr\ (s);\ \ \ \ \ \ \ E^{{^\circ}}\ = \ - \ 0.740\ V$ $2H^{+}\ \ \ (aq)\ + \ {2e}^{-}\ \ \longrightarrow \ H_{2}(g);\ \ \ \ \ \ E^{{^\circ}}\ = \ 0.00\ V$ ${Fe}^{3 +}\ (aq)\ + \ e^{-}\ \ \longrightarrow \ {Fe}^{2 +}(aq);\ \ \ \ \ E^{{^\circ}}\ = \ + \ 0.762\ V$ The strongest reducing agent is
A) Zn (s)
B) Cr (s)
C) $H_{2}$(g)
D) ${Fe}^{2 +}$(aq)
Explanation
(a)
The substances which have lower reduction potentials are stronger reducing agent. The reduction potential of zinc is lowest among these hence, it is the strongest reducing agent.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.