Question

What is a double decomposition reaction ?

Answer 1

A double decomposition reaction is a type of reaction in which two compounds in their aqueous solutions react to interchange their ions to form two new compounds.

$\mathrm{AB}+\mathrm{CD}\to \mathrm{AD}+\mathrm{BC}$

Let us understand it with an example-

$\underset{\mathrm{Sodium}\mathrm{chloride}}{\mathrm{NaCl}\left(\mathrm{aq}\right)}+\underset{\mathrm{Silver}\mathrm{nitrate}}{{\mathrm{AgNO}}_3\left(\mathrm{aq}\right)}\to \underset{\mathrm{Silver}\mathrm{chloride}}{\mathrm{AgCl}\left(\mathrm{s}\right)}+\underset{\mathrm{Sodiume}\mathrm{nitrate}}{{\mathrm{NaNO}}_3\left(\mathrm{aq}\right)}$

In the above reaction, two things are occurring-

• Chloride ion(Cl^-) is replacing Nitrate ion(NO₃^-).
• Nitrate ion(NO₃^-) is replacing Chloride ion(Cl^-).

Hence, the two different compounds are formed as products.