What is the relationship between the value of E⦵cell and the feasibility of the reaction?

The more positive the value of E⦵cell, the more feasible the redox reaction is.

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How does the E⦵ value correlate with the tendency of the redox system to proceed in the forward (reduction) direction?

A more positive (or less negative) E⦵ value indicates a stronger tendency for the redox system to proceed in the forward (reduction) direction.

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Zn2+(aq) + 2e- ⇌ Zn(s)   E⦵ = -0.76 V

Explain how the value of E changes for the redox system above when the concentration of Zn2+ increases to greater than 1 mol dm-3.

The position of equilibrium shifts to the right (favouring the reduction of Zn2+) according to Le Chatelier's principle. As a result, E becomes less negative.

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What is the Nerst equation at 298 K?

Ecell ​= E⦵+ z0.059​log10​[reduced species][oxidised species]​


Ecell = electrode potential under non-standard conditions (V).

E⦵ = electrode potential under standard conditions (V).

z = number of electrons transferred in the reaction.

[oxidised species] = concentration of oxidised species (mol dm-3).

[reduced species] = concentration of reduced species  (mol dm-3).

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What is the equation that links the standard Gibbs free-energy change (ΔG⦵) to the standard electrode potential (E⦵)?

ΔG⦵=−nFE cell⦵​


ΔG⦵ = standard Gibbe free-energy change (kJ mol-1)

n = number of moles of electrons transferred (mol)

F = Faraday constant (C mol-1)

E⦵cell = standard cell potential (V)

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What does the sign of the E⦵cell value indicate about the feasibility of a redox reaction under standard conditions?

  • Positive E⦵cell - the redox reaction is feabile.
  • Negative E⦵cell - the redox reaction is not feasible.

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What is the conventional direction for writing the equilibrium of a half-cell?

The equilibrium of a half-cell is written so that the forward reaction represents reduction, while the backward reaction represents oxidation.


For example, the conventional direction of the Zn/Zn2+ half-cell is shown below.

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What is the equation that links the standard cell potential (E⦵cell) to the standard reduction potentials of the reduced and oxidised species?

Ecell⊖​=Ereduced⊖​−Eoxidised⊖​

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How does the standard reduction potential (E⦵) of an electrode relate to its likelihood of being oxidised in an electrochemical cell?

The more negative (or less positive) the E⦵ value of an electrode, the more likely it is to be oxidised and become the anode (negative electrode) in an electrochemical cell.

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What is the electrochemical series?

The electrochemical series is a list of reduction half-equations ordered by their standard electrode potentials (E⦵ values).

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Zn2+(aq) + 2e- ⇌ Zn(s)   E⦵ = -0.76 V

Explain how the value of E changes for the redox system above when the concentration of Zn2+ decreases to less than 1 mol dm-3.

The position of equilibrium shifts to the left (favouring the oxidation of Zn) according to Le Chatelier's principle. As a result, E becomes more negative.

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