Solubility of the sulphates. (iii) Sulphates. Lattice Energy. 1 litre of pure water will dissolve about 1 gram of calcium hydroxide at room temperature. Also, the solubility increases as we move down the group. Contents Thermal stability. So sulphates and carbonates become less soluble as you go down the Group; hydroxides become more soluble. Sulphates of both group 1 and group 2 metals are stable towards heat. There should be no precipitates in Group 1, indicating that all Group 1 carbonates and sulphates are soluble. Again, the hydration enthalpy decreases the same way as it does in the case of Group 2 cations bonded to OH⁻ ions. The table below provides information on the variation of solubility of different substances (mostly inorganic compounds) in water with temperature, at one atmosphere pressure.Units of solubility are given in grams per 100 millilitres of water (g/100 ml), unless shown otherwise. By contrast, the least soluble Group 1 carbonate is lithium carbonate. Unfortunately, the enthalpy of solution values for the Group 1 chlorides as calculated above don't agree with the values given in the same Data Book: SOLUBILITY OF COMPOUNDS (GROUP 1) Solubility of a compound mainly depends on two factors . Your answer would need to include: For sulphates: Solubility decreases as you go down the group. Barium hydroxide is soluble enough to be able to produce a solution with a concentration of around 0.1 mol dm-3 at room temperature. For Group 2, magnesium sulphate is soluble while strontium and barium sulphates are insoluble. Magnesium carbonate (the most soluble Group 2 carbonate) has a solubility of about 0.02 g per 100 g of water at room temperature. Problems with the data. - Sodium sulphate 0.5 mol dm –3. Carbonates of alkaline earth metals are insoluble in water. A question asking about the solubility of the Group 2 sulphates would probably ask you to state and explain the trend in solubilities of the sulphates of Group 2 elements. Observations . The sulphates become less soluble as you go down the Group. The sulphate of alkaline earth metals is less soluble. The substances are listed in alphabetical order. Since the hydration enthalpy decreases faster than the lattice enthalpy in the case of Group 2 sulphates, the solubility of Group 2 sulphates decreases while progressing down the group. They are : 1.Heat of Hydration (Hydration Energy) and 2. Problems with the usual explanations. The solubilities of these salts further increase on descending the group.Sulphates: Thermal stabilityThe sulphates of group-1 and group-2 metals are all thermally stable.solubility: sulphates of alkali metals are soluble in water. Group 2 carbonates are virtually insoluble in water. However, sulphates of alkaline earth metals show varied trends. A saturated solution has a concentration of about 1.3 g per 100 g of water at 20°C. Solubility. Sulphates of alkali metals are soluble in water.