Question

What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube? What type of reaction is this?

Answer 1

Double displacement reaction

• The reaction in which there is an exchange of ions between the reactants is called a double displacement reaction.
• The general reaction is as follows,
• $\mathrm{AB}+\mathrm{CD}\to \mathrm{AD}+\mathrm{CB}$

Example

• The reaction of potassium iodide $\left(\mathrm{KI}\right)$ with lead nitrate $\left(\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\right)$ solution gives potassium nitrate $\left({\mathrm{KNO}}_3\right)$ and lead iodide $\left({\mathrm{PbI}}_2\right)$ as the product and a yellow precipitate of lead iodide is observed, considering the reaction to be an example of precipitation reaction as well.
• The chemical reaction is as follows,
• $2\mathrm{KI}\left(\mathrm{aq}\right)+\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)\to 2{\mathrm{KNO}}_3\left(\mathrm{aq}\right)+{\mathrm{PbI}}_2\left(\mathrm{s}\right)$

Since potassium iodide and lead nitrate reacts with an exchange of ions to form a precipitate thus, it is a double displacement reaction as well as precipitation reaction.