When ammonium hydroxide is added to solution (B) - Lead nitrate, a white ppt. is formed, which is insoluble in excess of ${\mathrm{NH}}_4\mathrm{OH}$ . White ppt. in lead hydroxide.
$\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\left(\mathit{a}\mathit{q}\right)+2{\mathrm{NH}}_4\mathrm{OH}\left(\mathit{a}\mathit{q}\right)\to$ $\underset{\mathrm{White}\mathrm{ppt}}{\mathrm{Pb}{\left(\mathrm{OH}\right)}_2}+2{\mathrm{NH}}_4{\mathrm{NO}}_3\left(\mathit{a}\mathit{q}\right)$
The cation is ${\mathrm{Pb}}^{2+}$.