Solubilities of the halides, nitrates, carbonates, sulfates, and some perchlorates of all the alkali metals and alkaline earth metals in methanol at room temperature have been determined. Hydroxides of the lighter alkaline earth metals are insoluble in water, but their solubility increases as the atomic number of the metal increases. For example, barium has more activity than strontium or calcium. SOLUBILITY RULES. ... insoluble and slightly soluble plus a good set of rules for solubility at the end of the file. Hydroxides of the lighter alkaline earth metals are insoluble in water, but their solubility increases as the atomic number of the metal increases. Many acid phosphates are soluble, i.e., Mg(H 2 PO 4) 2 and Ca(H 2 PO 4) 2. Sulfides are generally insoluble. The alkaline earth metals are soluble. We know that hydration energy and lattice energy are inversely proportional to the radii of the ions. Each rule has exceptions and the important ones are noted. Most of the precipitation reactions that we will deal with involve aqueous salt solutions. Cr 2 S 3 and Al 2 S 3 decompose and precipitate as hydroxides. 6. The most important slightly soluble substance is calcium hydroxide, Ca ... All alkali metal and alkaline earth (Be 2+, Mg 2+, Ca 2+, Sr 2 Data on some, such as cesium and rubidium fluoride, nitrate, carbonate, and sulfate, appear to be reported for the first time. If you study the periodic table, you will know compounds of the top element in a group are often different from the others. 1. most sulfates are soluble except BaSO4, Hg2SO4,PbSO4 and CaSO4 sulfate. Add 1 mL (about 25 drops or fill the well about 1⁄ 4 inch or 0.5 cm deep) of an alkaline earth metal chloride solution to each well in a horizontal row, as follows (see Figure 1): All alkali metals sulfide and alkaline earth metals sulfides are soluble in water and form colourless aqueous solutions. 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. Actually I have to tell you it ranges from “not very” to “almost completely insoluble”. so your answer becomes BaSO4