Electrochemistry

About this unit

Electrochemistry studies the link between chemical reactions and electrical energy. Galvanic cells turn the energy of spontaneous redox reactions into electricity, while electrolytic cells use electricity to drive non-spontaneous reactions. The unit explains electrode potentials, the Nernst equation, conductance of solutions, Faraday's laws, batteries, fuel cells and corrosion, all of which matter in industry, energy storage and the protection of metals.

Key ideas

• Galvanic cells, salt bridge, standard hydrogen electrode and standard electrode potentials.
• E°cell = E°cathode − E°anode and the electrochemical series.
• Nernst equation, ΔG° = −nFE°cell and the link with the equilibrium constant.
• Conductivity, molar conductivity, cell constant and Kohlrausch's law.
• Electrolysis, Faraday's laws and products at electrodes.
• Dry cell, mercury cell, lead storage battery, fuel cells and rusting of iron.

How to prepare

Learn the sign conventions: oxidation at the anode and reduction at the cathode in every cell. Practise numericals on E°cell, Nernst equation, ΔG°, molar conductivity and Faraday's laws, keeping careful track of n and units. Memorise the electrode reactions for the common batteries and the steps of rusting. Expect both numerical and reasoning questions.