Acid-base and redox reactions

Acid-base and redox reactions

Acid-base and redox reactions are both types of chemical change, but they answer different questions. In a simple aqueous acid-base reaction, an acid supplies H⁺ ions and a base can neutralise them; HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l) is a familiar example. In redox reactions, electrons are transferred and oxidation numbers change. Oxidation is loss of electrons or an increase in oxidation number; reduction is gain of electrons or a decrease in oxidation number. Redox always involves both processes because electrons lost by one species are gained by another.

Work it through

For Mg(s) → Mg²⁺(aq) + 2e⁻, magnesium loses electrons, so it is oxidised. In the linked reduction half-reaction, another species must gain those electrons. Do not decide redox only by noticing oxygen in a formula; use electron transfer or oxidation numbers when the evidence is available.

Mastery target

Classify an acid-base or redox process, use ions or oxidation numbers as evidence, and write a precise conclusion.