Q. The standard electrode potential for the half – cell reactions are ${Zn}^{2 +} + \ {2e}^{-}\ \longrightarrow Zn;\ E^{{^\circ}}$ = -0.76 V ${Fe}^{2 +} + \ {2e}^{-}\ \longrightarrow Fe;\ E^{{^\circ}}$ = -0.44 V The emf of the cell reaction, ${Fe}^{2 +} + \ Zn\ \longrightarrow {Zn}^{2 +} + \ Fe\$is
A) -0.32 V
B) -1.20 V
C) +1.20 V
D) +0.32 V
Explanation
(d)
${Zn}^{2 +} + \ {2e}^{-}\ \longrightarrow Zn;\ E^{{^\circ}}\ = \ - 0.76\ V$
${Fe}^{2 +} + \ {2e}^{-}\ \longrightarrow Fe;\ E^{{^\circ}}\ = \ - 0.44\ V$
Cell reaction is
${Fe}^{2 +} + \ Zn\ \longrightarrow {Zn}^{2 +} + \ Fe$
$E_{cell}^{{^\circ}} = \ E_{cathode}\ - \ E_{anode}$
= - 0.44 – (0.76)
= - 0.44 + 0.76
=0.32 V
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.