Question

What do you understand by a precipitation reaction? Explain with an example.

Answer 1

Precipitation reaction - A reaction in which two compounds in their aqueous solution react to form an insoluble salt as one of the products, this type of reaction is called a precipitation reaction.

Example - When copper sulphate solution reacts with hydrogen sulphide gas it forms a black precipitate of Copper sulphide and produces acid in an aqueous solution.

$$\begin{gathered} {\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{S}\left(\mathrm{g}\right)\to \mathrm{CuS}\left(\mathrm{s}\right)(\downarrow )+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right) \\ \mathrm{copper}\mathrm{sulphate}\mathrm{hydrogen}\mathrm{sulphide}\mathrm{copper}\mathrm{sulphide}\mathrm{sulphuric}\mathrm{acid} \end{gathered}$$