Name a salt which is insoluble in cold water and soluble in hot water.

1. Definition: Salt are the neutral compounds formed from the neutralisation reaction of an acid compound and a base compound.
2. Salts are generally soluble in water but there is an exception in salt for example Lead chloride (${\mathbf{PbCl}}_{\mathbf{2}}$). Lead chloride (${\mathbf{PbCl}}_{\mathbf{2}}$) is insoluble in cold water but on dissolving in hot water it breaks to give Lead ions (${\mathbf{Pb}}^{\mathbf{2}\mathbf{+}}$) and Chloride ions (${\mathbf{Cl}}^{\mathbf{-}}$).
3. The reaction is given below.
   $$\begin{gathered} {\mathrm{PbCl}}_2\left(\mathrm{s}\right)\stackrel{{\mathrm{H}}_2\mathrm{O}}{\to }{\mathrm{Pb}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right) \\ \mathrm{Lead}\mathrm{Lead}\mathrm{Chloride} \\ \mathrm{Chloride}\mathrm{ion}\mathrm{ion} \end{gathered}$$
4. Therefore, a salt which is insoluble in cold water and soluble in hot water is Lead chloride (${\mathbf{PbCl}}_{\mathbf{2}}$).