Question

Which of the following statements about the spontaneous reaction occurring in a galvanic cell is always true?
(A) ${{E}^{o}}_{cell}>0,\Delta {{G}^{0}}<0$ and $Q < K$
(B) ${{E}^{o}}_{cell}>0,\Delta {{G}^{0}}<0$ and $Q > K$
(C) ${{E}^{o}}_{cell}>0,\Delta {{G}^{0}}>0$ and $Q < K$
(D) ${{E}_{cell}}>0,\Delta {{G}^{0}}<0$ and $Q < K$

Answer 1

A galvanic cell is a device that can generate electric energy from chemical energy. Electrical energy brings out a chemical reaction with the help of an external energy source. Both the anode and cathode are in the same container with an electrolyte solution. The reaction which produces electricity in a galvanic cell is spontaneous.

Complete Solution :
In a galvanic cell, the standard electrode potential for redox reaction is positive than the reaction in the galvanic cell proceeds in the forward direction, which is known as a spontaneous process in a galvanic cell.
For standard electrochemical cells,
The standard electrode potential of a redox reaction is positive means, ${{E}^{o}}_{cell}>0$-- (1)
Spontaneous redox reactions in a galvanic cell can be used to produce electricity.
In a galvanic cell, the relation between Gibbs free energy and standard emf of a cell,
$\Delta {{G}^{0}}=-nF{{E}^{0}}_{cell}$
Here, n = number of moles, F = faraday constant

If ${{E}^{o}}_{cell}>0$, then $\Delta {{G}^{o}}<0$ which indicates the process in a galvanic cell is spontaneous.
If $\Delta {{E}^{o}}<0$ , then $\Delta {{G}^{o}}>0$ which represents the process in an electrolytic cell is non-spontaneous.
Hence, in a galvanic cell, the change in Gibbs free energy is positive when a spontaneous redox reaction drives the cell to produce an electric potential.
If the reaction is spontaneous then Q < K
So, the spontaneous reaction occurring in a galvanic cell is ${{E}^{o}}_{cell}>0,\Delta {{G}^{0}}<0$ and $Q < K$
So, the correct answer is “Option A”.

Note: If the standard emf of a cell is negative, then the reaction will not proceed in the forward reaction which indicates a non-spontaneous process. These reactions will be a spontaneous reaction in the reverse direction and non-spontaneous redox reactions cannot produce the electricity.