Classifying a Reaction as Precipitation, Acid-Base, or Redox

Classifying a reaction means checking, in order, whether ions combine to form an insoluble solid, whether a hydrogen ion transfers between species, or whether any oxidation number changes.

A reaction between silver nitrate and sodium chloride forms solid AgCl with no charge changes on any element — a precipitation reaction. A reaction between HCl and NaOH transfers H+ from acid to base with no oxidation-number changes — an acid-base reaction. A reaction between zinc metal and copper sulfate changes zinc's oxidation number from 0 to +2 and copper's from +2 to 0 — a redox reaction, specifically single-displacement.