NEETChemistryElectrochemistry
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): For the concentration cell Pt | H₂(1 bar ) | H^+(pH=3) || H^+(pH=2) | H₂(1 bar ) | Pt , the cell potential is positive. Reason (R): In a concentration cell, the cell potential is positive if the concentration of the active ion in the cathodic half-cell is greater than that in the anodic half-cell.
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
For a hydrogen concentration cell, the net cell reaction is: H^+( cathode ) H^+( anode ) Using the Nernst equation at 298 K : E_ cell = E^ _ cell - 0.059 1 [H^+]_ anode [H^+]_ cathode Since E^ _ cell = 0 for a concentration cell, E_ cell will be positive only if [H^+]_ anode [H^+]_ cathode [H^+]_ anode . Thus, Reason (R) is correct. Evaluating Assertion (A): At the anode, pH = 3 [H^+]_ anode = 10⁻³ M At the cathode, pH = 2 [H^+]_ cathode = 10⁻² M Since [H^+]_ cathode > [H^+]_ anode , the cell potential E_ cell is p