Question

A galvanic cell behaves as an electrolytic cell when?

• A. \( E_{\text{cell}} = E_{\text{ext}} \)
• B. \( E_{\text{cell}} = 0 \)
• C. \( E_{\text{ext}}>E_{\text{cell}} \)
• D. \( E_{\text{cell}}>E_{\text{ext}} \)

Hint:

When an external voltage greater than the cell potential is applied, the galvanic cell functions as an electrolytic cell.

Answer 1

The Correct Option is C

The question is about when a galvanic cell behaves like an electrolytic cell. To answer this, we need to understand the functioning of both types of cells:

• Galvanic Cell (or Voltaic Cell): This type of cell generates electrical energy from spontaneous chemical reactions. It always has a positive cell potential (\(E_{\text{cell}}\)) which drives the flow of electrons.
• Electrolytic Cell: This type of cell requires an external electrical energy source to drive non-spontaneous chemical reactions. This process occurs when the external voltage is greater than the cell potential of the galvanic cell.

Thus, a galvanic cell behaves as an electrolytic cell when an external voltage (\(E_{\text{ext}}\)) that exceeds the naturally occurring cell potential (\(E_{\text{cell}}\)) is applied. In this case, the direction of electron flow is reversed by the external source, making the non-spontaneous reaction occur in the cell.

Let's justify the options:

• \(E_{\text{cell}} = E_{\text{ext}}\): This would lead to no net current flow, and the system would be at equilibrium, not functioning as an electrolytic cell.
• \(E_{\text{cell}} = 0\): Indicates that there is no potential difference driving reactions in the cell, which is not relevant to switching cell functions.
• \(E_{\text{ext}}>E_{\text{cell}}\) (Correct Answer): The external voltage is greater than the cell's own potential, causing it to function as an electrolytic cell.
• \(E_{\text{cell}}>E_{\text{ext}}\): The cell would continue to function as a galvanic cell, not electrolytic.