Redox and Electrochemistry

This lesson covers oxidation states, redox reactions, half-equations, standard electrode potentials, electrochemical cells, electrolysis, Faraday's laws, disproportionation, and the effect of non-standard conditions. Electrochemistry connects chemical energy to electrical energy and is central to understanding batteries, fuel cells, electrolysis, and corrosion.

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Oxidation and Reduction

Key Definition: Oxidation is the loss of electrons (or an increase in oxidation state). Reduction is the gain of electrons (or a decrease in oxidation state). The two always occur together — a redox reaction.

Concept	Oxidation	Reduction
Electrons	Loss	Gain
Oxidation state	Increases	Decreases
Oxygen	Gain	Loss
Hydrogen	Loss	Gain

The mnemonic OILRIG helps: Oxidation Is Loss, Reduction Is Gain (of electrons).

An oxidising agent (oxidant) is a substance that causes oxidation by accepting electrons — it is itself reduced. A reducing agent (reductant) causes reduction by donating electrons — it is itself oxidised.

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Oxidation States (Oxidation Numbers)

Oxidation states are assigned using a set of rules: