1. most sulfates are soluble except BaSO4, Hg2SO4,PbSO4 and CaSO4 sulfate. Solubility Patterns in the Periodic Table continued 2 216 linn Scientiic nc ll ihts esered 4. Solubility of sulfates generally decrease as you go down a group. Those of the alkali metals and ammonium ion are soluble. Solubility of sulphates: The solubility of sulphates of alkaline earth metals decreases as we move down the group from Be to Ba due to the reason that ionic size increases down the group. All alkali metals sulfide and alkaline earth metals sulfides are soluble in water and form colourless aqueous solutions. Many acid phosphates are soluble, i.e., Mg(H 2 PO 4) 2 and Ca(H 2 PO 4) 2. This question illustrates it well. For example, barium has more activity than strontium or calcium. Most of the precipitation reactions that we will deal with involve aqueous salt solutions. Colours of metal sulfides are important in identifying compounds in inorganic chemistry. The alkaline earth metals are soluble. Solubility of sulphates and carbonates of alkaline earth metals decreases as the atomic number of the metal increases down the group because the size of the cation increases down the group. We know that hydration energy and lattice energy are inversely proportional to the radii of the ions. Sulfides are generally insoluble. Hydroxides of the lighter alkaline earth metals are insoluble in water, but their solubility increases as the atomic number of the metal increases. so your answer becomes BaSO4