Among the given compounds, mercurous chloride is insoluble in water. The following compounds are always soluble in water :
(i) salts of IA group elements and $NH _{4}^{+}$ions.
(ii) All nitrate, acetate and perchlorate $\left( ClO _{4}^{-}\right)$ compounds.
(iii) All sulphate compounds (except those of $Ca ^{2+}, Sr ^{2+}, Ba ^{2+}$ and $\left.Pb ^{2+}\right)$.
(iv) All chloride compounds (except those of $Ag ^{+}, Pb ^{2+}, Cu ^{+}$and $\left.Hg _{2}^{2+}\right)$.