Question

Lead nitrate solution is added to the test tube containing Potassium iodide solution. $\left(\mathrm{i}\right)$ Write the name and color of the compound precipitated. $\left(\mathrm{ii}\right)$Write the balanced chemical equation for the reaction involved $\left(\mathrm{iii}\right)$Name the type of reaction justifying your answer.

Answer 1

The reaction of Lead nitrate and Potassium iodide.

1. Precipitation is a reaction that results in the formation of insoluble solid material.
2. Iodide ion displaces Nitrate from Lead nitrate and Nitrate displaces iodine from Potassium iodide when aqueous Lead nitrate is reacted with Potassium iodide. As a result, two new products are formed: Potassium nitrate and Lead iodide. $\underset{\mathrm{Lead}\mathrm{nitrate}}{\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Potassium}\mathrm{iodide}}{2\mathrm{KI}\left(\mathrm{aq}\right)}\to \underset{\underset{(\mathrm{Yellow}\mathrm{colour})}{\mathrm{Lead}\mathrm{iodide}\left(\mathrm{precipitated}\right)}}{{\mathrm{PbI}}_2\left(\mathrm{s}\right)\downarrow }+\underset{\mathrm{Potassium}\mathrm{nitrate}}{2{\mathrm{KNO}}_3\left(\mathrm{aq}\right)}$
3. The precipitate formed is the compound Lead iodide of yellow color.
4. The presence of yellow Lead iodide particles in the reaction mixture shows that a chemical transition has occurred.

Chemical Equation for the formation of Lead iodide:

1. When aqueous Lead nitrate is added to Potassium iodide, the iodide ion displaces the nitrate ion, and the Nitrate ion displaces the iodine ion. Two new compounds are produced as a result: potassium nitrate and lead iodide.$\underset{\mathrm{Lead}\mathrm{nitrate}}{\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Potassium}\mathrm{iodide}}{2\mathrm{KI}\left(\mathrm{aq}\right)}\to \underset{\underset{(\mathrm{Yellow}\mathrm{colour})}{\mathrm{Lead}\mathrm{iodide}\left(\mathrm{precipitated}\right)}}{{\mathrm{PbI}}_2\left(\mathrm{s}\right)\downarrow }+\underset{\mathrm{Potssium}\mathrm{nitrate}}{2{\mathrm{KNO}}_3\left(\mathrm{aq}\right)}$
2. Among Potassium nitrate and lead iodide, Lead iodide s the precipitate formed.

Double displacement reaction:

1. Double displacement reactions are those in which two chemicals react by exchanging ions to produce two new molecules.
2. Iodide ion displaces nitrate from Lead nitrate and Nitrate displaces iodine from Potassium iodide when aqueous Lead nitrate is introduced to Potassium iodide. Resulting in two new products Potassium nitrate and Lead iodide.$\underset{\mathrm{Lead}\mathrm{nitrate}}{\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2}+\underset{\mathrm{Potassium}\mathrm{iodide}}{2\mathrm{KI}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Lead}\mathrm{iodide}}{{\mathrm{PbI}}_2\left(\mathrm{s}\right)\downarrow }+\underset{\mathrm{Potassium}\mathrm{nitrate}}{2{\mathrm{KNO}}_3\left(\mathrm{aq}\right)}$
3. Here, the Iodide ion and Nitrate ion are replaced, hence it is a double displacement reaction.