Question

State what will you observe when lead nitrate crystals are heated in a dry test tube.

Answer 1

1. Decomposition reaction definition: The reaction where a single reactant compound splits in two or more than two product compounds by physical or chemical act is termed as a decomposition reaction.
2. Lead nitrate( $\mathbf{Pb}{\mathbf{\left(}{\mathbf{NO}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{2}}$) is a white salt which on heating under flame forms a yellow precipitate of Lead oxide ($\mathbf{PbO}$), Nitrogen gas (${\mathbf{N}}_{\mathbf{2}}$) and Oxygen gas (${\mathbf{O}}_{\mathbf{2}}$) as a product.
3. Brown fumes are liberated during the reaction indicating the formation of Nitrogen gas (${\mathbf{N}}_{\mathbf{2}}$).
4. The decomposition reaction of Lead nitrate ($\mathbf{Pb}{\mathbf{\left(}{\mathbf{NO}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{2}}$) is shown below.
   $$\begin{gathered} 2\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{s}\right)\stackrel{∆}{\to }2\mathrm{PbO}\left(\mathrm{s}\right)+4{\mathrm{NO}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right) \\ \mathrm{Lead}\mathrm{Lead}\mathrm{Nitrogen}\mathrm{Oxygen} \\ \mathrm{nitrate}\mathrm{oxide}\mathrm{dioxide} \end{gathered}$$
5. Therefore, the two observations made when Lead nitrate ($\mathbf{Pb}{\mathbf{\left(}{\mathbf{NO}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{2}}$) crystals are heated in a dry test tube are the formation of a yellow precipitate of Lead oxide ($\mathbf{PbO}$) and liberation of brown fumes of Nitrogen dioxide (${\mathbf{NO}}_{\mathbf{2}}$).