JEE Main · 2023 · Shift-IImediumTHERMO-132

The incorrect statements from the following is:

Thermodynamics · Class 11 · JEE Main Previous Year Question

Question

The incorrect statements from the following is:

Options
  1. a

    A. The electrical work that a reaction can perform at constant pressure and temperature is equal to the reaction Gibbs energy.

  2. b

    B. Ecell∘E^\circ_{\text{cell}} is dependent on the pressure.

    ✓
  3. c

    C. dEcelldT=ΔrS∘nF\frac{dE_{\text{cell}}}{dT} = \frac{\Delta_r S^\circ}{nF}

  4. d

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

Correct Answerb

B. Ecell∘E^\circ_{\text{cell}} is dependent on the pressure.

Detailed Solution

🧠 Ecell∘E^\circ_{\text{cell}} is a standard-state quantity — it is defined at fixed conditions and does not vary with external pressure Standard EMF is measured at 1 bar and a specified temperature. Since pressure is already fixed in the definition of "standard state," saying Ecell∘E^\circ_{\text{cell}} changes with pressure is self-contradictory.

Evaluating the other statements:

  • (A) Correct — electrical work at constant T,PT,P equals −ΔrG-\Delta_r G.
  • (C) Correct — the temperature coefficient of cell potential is dE/dT=ΔrS∘/nFdE/dT = \Delta_r S^\circ / nF.
  • (D) Correct — reversible cell operation requires balanced opposing EMF.

Statement (B) is false: Ecell∘E^\circ_{\text{cell}} does not depend on pressure because it is the standard value defined at 1 bar.

Answer: (b)\boxed{\text{Answer: (b)}}

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