Electrochemical Cells and Electrode Potential — Part 2: Electrochemical series and the Nernst equation: visual lesson, ISC Class 12 Chemistry

Lesson

Electrode potentials at work

Part 2 — ranking electrodes, predicting reactions and correcting for concentration.

In this lesson you will

Predict how electrode potential changes with concentration, temperature and the nature of the electrode
Use the electrochemical series to predict displacement reactions and calculate standard cell emf
Calculate the emf of a cell at non-standard concentrations using the Nernst equation
Calculate ΔG° and the equilibrium constant from the standard cell emf

Concept

Factors affecting electrode potential

For $\ce{M^{n+} + ne- <=> M}$ : (1) Concentration of ions: increasing [Mⁿ⁺] shifts the equilibrium right and makes the reduction potential more positive (Le Chatelier; Nernst). (2) Temperature: E changes with T (the Nernst factor 2.303RT/nF grows with T). (3) Nature of the electrode: metals that lose electrons easily (low ionisation enthalpy, high hydration enthalpy of the ion) have more negative reduction potentials.

Cu²⁺/Cu at 298 K

Slope = 0.059/n = 0.0295 V per tenfold change in concentration (n = 2).

Check your understanding

Quick check: factors affecting E

Predict how an electrode potential changes when the ion concentration changes.

Question: Multiple choice

Multiple choice1 mark

The concentration of Cu²⁺ in a copper half-cell is increased from 0.01 M to 0.1 M at 298 K. The reduction potential of the electrode:

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