The number of incorrect statements from the following is _______
A. The electrical work that a reaction can perform at constant pressure and temperature is equal to the reaction Gibbs energy.
B. E0cell is dependent on the pressure

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D. A cell is operating reversibly if the cell potential is exactly balanced by an opposing source of potential difference.

Answer: 1
Option B is indeed the incorrect statement among the given options, and the rest of the statements (A, C, and D) are correct. Let’s explain the correctness of each statement:

A. This statement is correct. The Gibbs free energy (∆G) of a chemical reaction at constant pressure and temperature is a measure of the maximum non-expansion work that the reaction can perform. It accounts for both the enthalpy change (∆H) and the entropy change (∆S) of the system.

B. This statement is incorrect. The standard cell potential (E0 cell) is typically considered independent of pressure in electrochemical reactions. It is defined under standard conditions, which include a reference pressure (usually 1 bar or 1 atm). Changes in pressure can affect the equilibrium constant (K) and the reaction quotient (Q) but generally do not have a significant impact on E0 cell.

C. This statement is correct. It relates the change in cell potential (E0 cell) with temperature to the standard entropy change (∆rS0) in a chemical reaction, where n is the number of moles of electrons transferred, and F is the Faraday constant.

D. This statement is correct. In electrochemistry, a cell is operating reversibly when its electromotive force (cell potential, E0 cell) is exactly balanced by an opposing potential difference, typically provided by an external source, so no net current flows. This is a fundamental concept in electrochemical thermodynamics. So, only option B is incorrect, and the other statements (A, C, and D) are accurate.

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