Question

Explain, giving one simple example of the following chemical changes

Double decomposition

Answer 1

Double displacement or double decomposition reaction

• It is a chemical reaction in which two compounds in their aqueous solutions react to form two new compounds by the mutual exchange of their radicals.
• In general double decomposition reaction can be represented as
• $\mathrm{AB}+\mathrm{CD}\stackrel{}{\to }\mathrm{AD}+\mathrm{BC}$
• For example when barium chloride $\left({\mathrm{BaCl}}_2\right)$ reacts with sulphuric acid$\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$, they undergo mutual exchange of their radicals resulting in the formation of barium sulphate$\left({\mathrm{BaSO}}_4\right)$ and hydrochloric acid$\left(\mathrm{HCl}\right)$.
• $\underset{\mathrm{Barium}\mathrm{chloride}}{{\mathrm{BaCl}}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Sulphuric}\mathrm{acid}}{{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)}\stackrel{}{\to }\underset{\mathrm{Barium}\mathrm{sulphate}}{{\mathrm{BaSO}}_4\left(\mathrm{s}\right)\downarrow }+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{aq}\right)}$
• The above reaction is also a precipitate reaction.