10. Calcium sulfide (CaS) is insoluble in water: Why ? would positive because the ion-dipole interactions are If CaS were to dissolve. ΔH very weak compared to the ion-ion interactions being overcome. Salts containing Ca2+ are never soluble in water. The covalent bonds in CaS would require a great deal of energy to overcome upon dissolving. If CaS were to dissolve, ΔS would be negative because the possible arrangements for the water molecules would decrease.