Question

How is a base prepared by double decomposition? Explain, giving an example.

Answer 1

A base can be prepared by double decomposition when a soluble salt reacts with another soluble compound, resulting in the formation of an insoluble base (hydroxide) as a precipitate.

Example:

When sodium hydroxide reacts with copper(II) sulphate, insoluble copper(II) hydroxide is formed:

\[\ce{CuSO4 + 2NaOH -> Cu(OH)2 ↓ + Na2SO4}\]

Here, Cu(OH)₂ is the base formed as a precipitate.