Question

The standard electrode potential for Daniell cell is 1.1 V. The standard Gibbs free energy for the reaction Zn(s) + Cu$^{2+}$(aq) → Zn$^{2+}$(aq) + Cu(s) is approximately:

• A. -212.27 J/mol
• B. -21.22 J/mol
• C. -212271.4 J/mol
• D. -2.1227 J/mol

Answer 1

The Correct Option is A

The standard Gibbs free energy change (ΔG°) is calculated using the relationship between Gibbs free energy and standard electrode potential (E°):

ΔG° = -nFE°

Definitions:

• n = moles of electrons exchanged in the balanced equation.
• F = Faraday's constant = 96485 C/mol.
• E° = standard electrode potential = 1.1 V.

For the reaction Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s), n = 2, representing the electron transfer from Zn⁰ to Zn²⁺ and Cu²⁺ to Cu⁰. Substituting values:

ΔG° = -2 × 96485 × 1.1

ΔG° = -212267 J/mol

To convert to kJ/mol for option matching:

ΔG° = -212.27 kJ/mol

Therefore, the standard Gibbs free energy change for the reaction is approximately -212.27 kJ/mol, aligning with the provided correct answer.