Question

Give two examples of double displacement reactions with their chemical equations.

Answer 1

Double displacement reaction

• A double displacement reaction is a type of chemical reaction in which positive and negative radicals of two reactants are exchanged which will lead to the formation of the product.
• These reactions are very fast, and the product is formed as soon as the reactants come into contact.
• They are represented as a reaction

AB + CD $\to$AD + BC

• There are two types of double displacement reactions which are precipitation reactions and neutralization reactions.

(A) Precipitation reaction: This type of double displacement reaction usually takes place in solution. One of the products formed from precipitation reaction is an insoluble or nearly insoluble solid and the precipitate is formed as soon as the reactants come into contact.

Example: Reaction between $\mathrm{Silver}\mathrm{nitrate}\left({\mathrm{AgNO}}_3\right)$and $\mathrm{Sodium}\mathrm{chloride}\left(\mathrm{NaCl}\right)$ is leads to the formation of a precipitate $\mathrm{Silver}\mathrm{chloride}\left(\mathrm{AgCl}\right)$ and $\mathrm{Sodium}\mathrm{nitrate}\left({\mathrm{NaNO}}_3\right)$.

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

(B)Neutralisation reaction: The neutralization reaction is also a kind of double displacement reaction in which an acid reacts with a base to form salt and water.The product salt contains anion from acid and cation from the base.

Example: Solution of $\mathrm{Sodium}\mathrm{hydroxide}\left(\mathrm{NaOH}\right)$ reacts with dilute $\mathrm{Hydrochloric}\mathrm{acid}\left(\mathrm{HCl}\right)$ to form the salt $\mathrm{Sodium}\mathrm{chloride}\left(\mathrm{NaCl}\right)$and water. $\underset{\mathrm{Sodium}\mathrm{hydroxide}}{\mathrm{NaOH}\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Sodium}\mathrm{chloride}}{\mathrm{NaCl}\left(\mathrm{aq}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$