Question

The standard emf of a cell Zn/Zn\(^{2+}\) || Fe\(^{2+}\)/Fe if electrode potentials for (Zn/Zn\(^{2+}\)) and (Fe\(^{2+}\)/Fe) are 0.763 V and -0.44 V respectively is

• A. +0.323 V
• B. -1.203 V
• C. +1.203 V
• D. -0.323 V

Hint:

Positive EMF indicates spontaneous reaction.

Answer 1

The Correct Option is A

To find the standard emf of the cell Zn/Zn²⁺ || Fe²⁺/Fe, we need to use the standard electrode potentials given for each half-cell reaction. The emf of the cell can be calculated using the formula:

\(E_{\text{cell}} = E_{\text{cathode}} - E_{\text{anode}}\)

For the given cell:

• Zn/Zn²⁺ is the anode, with an electrode potential, \(E_{\text{anode}} = -0.763 \, \text{V}\)
• Fe²⁺/Fe is the cathode, with an electrode potential, \(E_{\text{cathode}} = -0.44 \, \text{V}\)

Substituting these values into the formula:

\(E_{\text{cell}} = -0.44 \, \text{V} - (-0.763 \, \text{V})\)

This simplifies to:

\(E_{\text{cell}} = -0.44 \, \text{V} + 0.763 \, \text{V} = 0.323 \, \text{V}\)

Hence, the standard emf of the cell is +0.323 V.

The correct answer is +0.323 V.