Double Displacement Reaction
A reaction in which two compounds exchange partner ions to form two new compounds.
Formula / equation
AB + CD → AD + CB
Unit
Dimensionless
In depth
Also called metathesis, these reactions occur only when one product leaves the solution — as a precipitate, a gas or a weak electrolyte such as water. If every possible product is soluble and strong, no net reaction occurs and the ions simply remain mixed.
Examples in the real world
AgNO₃ + NaCl → AgCl↓ + NaNO₃; Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂↑.