Question

For the feasibility of a redox reaction in a cell, the emf of the cell should be:

• A. Zero
• B. Positive
• C. Negative
• D. Fixed

Answer 1

The correct option is B Positive

Any redox reaction would occur spontaneously if the free energy change, $\left(\Delta G\right)$ is negative.

Relation between $\Delta G$ and $E_{cell}$ is

$-\Delta G=nF{E}_{cell}$
At standard condition,
$\Delta G^0=nF{E}_{cell}^0$

where,
n is the number of electrons involved in the reaction.
F is the Faraday constant
$E^0$ is the cell emf

If $\Delta G^0$ is negative, then the $E^0$ value will be positive.
Thus, for a feasible redox reaction, emf of the cell should be positive.