Question

Which of the following metals will couple to provide a higher cell potential for a galvanic cell?
$Z{n}^{2+}\left(aq\right)+2e^{-}\to Zn\left(s\right);E^0=-0.76V$
$C{u}^{2+}\left(aq\right)+2e^{-}\to Cu\left(s\right);E^0=0.34V$
$N{i}^{2+}\left(aq\right)+2e^{-}\to Ni\left(s\right);E^0=-0.25V$
$P{b}^{2+}\left(aq\right)+2e^{-}\to Pb\left(s\right);E^0=-0.13V$
$F{e}^{2+}\left(aq\right)+2e^{-}\to Fe\left(s\right);E^0=-0.44V$

• A. Zinc and copper
• B. Zinc and Nickel
• C. Lead and copper
• D. Zinc and Iron

Answer 1

The correct option is A Zinc and copper

Standard reduction potentials (SRP) of the half cell electrodes are calculated and arranged in a series of increasing order which is known as electrochemical series.
The standard electrode potential of $H^{+}/H_2$ couple is zero.

Here, a negative $E^0$ signifies that it has high tendency to get oxidised and the redox couple is a stronger reducing agent than the $H^{+}/H_2$ couple.

A positive $E^0$ signifies that it has high tendency to get reduced and the redox couple is a stronger oxidising agent than the $H^{+}/H_2$ couple.

Electrochemical series helps in the selection of electrode assemblies to construct the galvanic cells of desired EMFs.

For a galvanic cell to provide high cell voltage, the half cell having higher reduction potential and lower reduction potential should be connected.

Here, $Z{n}^{2+}/Zn$ has the lowest standard reduction potential and $C{u}^{2+}/Cu$ has the highest reduction potential.
Hence, these metals will couple to provide a higher cell potential.