Question

Potential at the equivalence point for a redox reaction
\(\mathrm{aOX1} + \mathrm{bRED2} \rightleftharpoons \mathrm{bOX2} + \mathrm{aRED1}\)
is given by the equation:

• A. \(E=\frac{(bE_1^0+aE_2^0)}{(a+b)}\)
• B. \(E=E^0+(\frac{0.0592}{n})X logQ\)
• C. \(E=E^0+(\frac{0.0592}{n})X log(\frac{Red}{OX})\)
• D. \(E=E_1^0+\frac{E_2^0}{2}\)

Answer 1

The Correct Option is A

To determine the potential at the equivalence point for a redox reaction, we need to understand the standard electrode potential concepts and how they are combined for a redox reaction at equivalence.

The given redox reaction is: 

\(\mathrm{aOX1} + \mathrm{bRED2} \rightleftharpoons \mathrm{bOX2} + \mathrm{aRED1}\)

At the equivalence point of a redox titration, the concentrations of oxidized and reduced species are such that the half equations for the two reactions have been combined to reach a balanced equation. The cell potential at this point is a weighted average of the standard electrode potentials of the two half-reactions involved. The formula for calculating the cell potential at the equivalence point for a redox titration is:

\(E=\frac{(bE_1^0+aE_2^0)}{(a+b)}\)

Here's the reasoning for selecting this formula:

1. Weighted Average: In a balanced redox reaction at the equivalence point, the potentials of the participating reactions need to be averaged according to their stoichiometric coefficients. The formula represents this weighted average of potentials, taking into account the stoichiometry of the reactants and products.
2. Options Analysis:
   • Option 1: \(E=\frac{(bE_1^0+aE_2^0)}{(a+b)}\) - This is the correct formula representing the weighted average for the redox equivalence point, considering standard conditions.
   • Option 2: \(E=E^0+\left(\frac{0.0592}{n}\right)\log Q\) - This equation represents the Nernst equation where \(Q\) is the reaction quotient. This applies to non-standard conditions but not directly to calculating the equivalence point potential.
   • Option 3: \(E=E^0+\left(\frac{0.0592}{n}\right)\log\left(\frac{Red}{OX}\right)\) - Similar to the Nernst equation, this relates cell potential to the concentration of reduced and oxidized species but is not specific for equivalence point calculation in terms of standard potentials.
   • Option 4: \(E=E_1^0+\frac{E_2^0}{2}\) - Incorrect as it does not account for stoichiometric coefficients.

Considering the analysis and explanation, the correct answer is:

\(E=\frac{(bE_1^0+aE_2^0)}{(a+b)}\)