JEE Main Chemistry Question (2026) — Solution

Step-by-step solution

The standard cell potential E^ _ cell is a thermodynamic property defined for a cell under standard conditions (concentrations of all species at 1 M , pressure at 1 bar , and a specific temperature). For a Daniell cell, the reaction is Zn(s) + Cu^ 2+ (aq) Zn^ 2+ (aq) + Cu(s). The standard cell potential is given by E^ _ cell = E^ _ Cu^ 2+ /Cu - E^ _ Zn^ 2+ /Zn . Since E^ _ cell depends only on the nature of the electrodes, the nature of the electrolytes, and the temperature, it remains constant over time as long as the temperature is constant. While the actual cell potential E_ cell changes as the reaction proceeds (due to changes in concentration according to the Nernst equation), the standard cell potential E^ _ cell is a constant value. Therefore, the plot of E^ _ cell versus time is a horizontal line parallel to the time axis.