Thread: decrease in lattice energy and hydration energy means more positive or negative if to explain solubility of group 2 sulphate.

decrease in lattice energy and hydration energy means more positive or negative if to explain solubility of Group2 sulphate?

Originally Posted by BenYeohYeelon

decrease in lattice energy and hydration energy means more positive or negative if to explain solubility of Group2 sulphate?

There is an explanation of lattice energy here: Lattice energy - Wikipedia, the free encyclopedia

If you are using the modern convention, the lattice energy should be defined as negative, i.e. the amount by which the lattice has a lower energy (is more stable) than free ions at infinite separation.

Hydration energy is described here: Hydration energy - Wikipedia, the free encyclopedia

This actually deals specifically with the issue of whether salts are insoluble or not - though it describes it in rather black and white terms, as if a salt is either "soluble" or "insoluble", whereas in fact of course there is a whole spectrum of solubility in between.

Suggest an energy level diagram may be helpful, i.e. go in one step from crystal lattice to free ions and in another step hydrate them and see the net energy (enthalpy) change.

Of course, the position of the equilibrium between dissolved and undissolved salt will be determined not by enthalpy alone, but by Gibbs Free Energy, which takes into account the effects of entropy as well as enthalpy.