Question

A galvanic cell is set up from electrodes A and B Electrode A: \( \text{Cr}_2\text{O}_7^{2-} / \text{Cr}^{3+}, \, E^\circ_{\text{red}} = +1.33 \, \text{V} \) Electrode B: \( \text{Fe}^{3+} / \text{Fe}^{2+}, \, E^\circ_{\text{red}} = +0.77 \, \text{V} \) Which of the following statements is false?

• A. Standard e.m.f of the cell is 0.56 V
• B. Current will flow from electrode A to B in the external circuit
• C. A will act as cathode and have positive polarity
• D. None of these

Hint:

In a galvanic cell, current flows from the anode to the cathode in the external circuit. The standard e.m.f is the difference between the reduction potentials of the two electrodes.

Answer 1

The Correct Option is D

The standard e.m.f of the cell is given by: \[ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} = 1.33 \, \text{V} - 0.77 \, \text{V} = 0.56 \, \text{V} \] Current flows from anode to cathode, and the anode is where oxidation occurs, so electrode A (Cr) will act as the anode, and electrode B (Fe) will act as the cathode. Therefore, the given statements are true, making option (4) correct.