Redox half-reactions, anodes and cathodes
≈ 50 minRedox half-reactions, anodes and cathodes
A redox equation can be split into half-reactions to make electron transfer explicit. Oxidation half-reactions place electrons on the product side; reduction half-reactions place electrons on the reactant side. The anode is oxidation and the cathode is reduction in all electrochemical cells. In a galvanic cell, electrons leave the negative anode and travel through the external circuit to the positive cathode. In an electrolytic cell, an external power supply drives a non-spontaneous reaction and changes electrode signs, but not the oxidation-anode and reduction-cathode definitions. Track charge and atoms before combining half-reactions.
Work it through
Zn(s) → Zn²⁺(aq) + 2e⁻ is an oxidation half-reaction because electrons are produced. Cu²⁺(aq) + 2e⁻ → Cu(s) is reduction because electrons are consumed. Adding them gives Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s), with electrons cancelled. The number of electrons must match before the halves are added.
Mastery target
Identify and balance simple redox half-reactions, assign anode and cathode, and distinguish electron flow from conventional current description.
At which electrode does reduction occur?
Name the key chemistry term from Redox half-reactions, anodes and cathodes that best fits the explanation and visual model.
Which half-reaction is oxidation?
Which statement corrects a common misunderstanding in Redox half-reactions, anodes and cathodes?