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Calculate The Standard Potential Eo for The Following Non-Balanced Cell

Reviewed by Calculator Editorial Team

The standard potential (Eo) of a non-balanced electrochemical cell represents the maximum voltage that can be generated under standard conditions. This calculator helps determine Eo by accounting for the cell's redox reactions and the number of electrons transferred.

Introduction

When calculating the standard potential of a non-balanced electrochemical cell, we need to consider the reduction potentials of the half-reactions involved and adjust for the stoichiometric coefficients. The standard potential is calculated using the Nernst equation, which relates the cell potential to the activities of the reactants and products.

The cell notation is typically written as: Oxidized | Reduced, where the left side shows the oxidation and the right side shows the reduction. For non-balanced cells, we must balance the reactions before calculating the standard potential.

Standard Potential Formula

The standard potential (Eo) of a cell is calculated using the following formula:

Eo = Ered - Eox

Where:

  • Ered = Standard reduction potential of the reduction half-reaction
  • Eox = Standard reduction potential of the oxidation half-reaction

For non-balanced cells, we must first balance the redox reactions and adjust the potentials accordingly. The balanced equation must show the same number of electrons transferred in both half-reactions.

Calculation Process

To calculate the standard potential of a non-balanced cell:

  1. Write the oxidation and reduction half-reactions.
  2. Balance the half-reactions to ensure the same number of electrons are transferred.
  3. Find the standard reduction potentials for each half-reaction.
  4. Calculate the standard potential using the formula: Eo = Ered - Eox.

Note: Always ensure the half-reactions are balanced before calculating the standard potential. The number of electrons transferred must be equal in both reactions.

Worked Example

Let's calculate the standard potential for the following non-balanced cell:

Zn | Cu2+

The balanced half-reactions are:

  • Oxidation: Zn → Zn2+ + 2e⁻ (Eox = -0.76 V)
  • Reduction: Cu2+ + 2e⁻ → Cu (Ered = +0.34 V)

Using the formula:

Eo = Ered - Eox = 0.34 V - (-0.76 V) = 1.10 V

The standard potential for this cell is 1.10 volts.

FAQ

What is the standard potential of a cell?

The standard potential (Eo) is the maximum voltage that can be generated by an electrochemical cell under standard conditions (25°C, 1 atm pressure, and 1 M concentration).

How do I balance redox reactions for standard potential calculation?

Balance the number of electrons transferred in both half-reactions. Multiply the coefficients of the half-reactions to ensure the same number of electrons are involved.

What units are used for standard potential?

Standard potential is measured in volts (V).