# What is the relation between solubility and thermal stability? [closed]

The thermal stability of alkaline earth metals increases down the group for hydroxides i-e., Be(OH)2 is less stable than Ba(OH)2. The solubility also increases down the group for these compounds i-e., Be(OH)2 is less soluble in water as compared to Ba(OH)2. Hence for Hydroxides of group 2 elements the solubility and thermal stability trends are same i-e. Both increases down the group. But the solubility and thermal stability trends become inverse of each other for the "sulphates of group 2 elements". Does this mean that there is no relation between solubility and thermal stability?

• There's no reason to think there would be such relation, imo. – Mithoron Dec 31 '19 at 16:41

Just have a look on the Calcium salts made with the halogens (F, Cl, Br, I). There is a nice analogy among Cl, Br and I, but not F. Look ! The Calcium chloride $$\ce{CaCl2}$$, bromide $$\ce{CaBr2}$$ and iodide $$\ce{CaI2}$$ are all extremely soluble in water. They are all soluble in less than their weight of water. But calcium fluoride $$\ce{CaF2}$$ is among the least soluble product on Earth. The principal mineral for Fluoride is $$\ce{CaF2}$$, and it can be found everywhere at the surface of the Earth. If this mineral would have been at least a little soluble in water, the rains would have washed away this mineral in the geological times. Why is there such a huge difference between calcium fluoride and the other halogenides ? Nobody knows !