Understanding Solubility: KNO3 and Na2SO4 in Water

[PPonte]

Why does the solubility of KNO₃, in water, rises with increasing temperature and the solubility of Na₂SO₄ descreases?
Thank you.

 

[Gokul43201]

What are your thoughts ?

We can't help you unless you help yourself.

 

[PPonte]

I am sorry. I usually help people who do not present their thoughts, I never remeber those rules.

Here are my thoughts:
1. The dissolution of a salt involves two phases. First, the separation of the ions, which is endoenergetic because involves breaking of ionic bonds and, second, the solvatation, in this case, an hydration since the solvent is water, which is exoenergetic.

2. If the energy consumed in the first phase is greater than the energy freed in the second phase, the dissolution of the salt is globally endoenergetic. If the energy consumed in the first phase is minor than the energy freed in the second phase, the dissolution of the salt is globally exoenergetic.

Conclusion: I think, then, that the dissolution of KNO3 is globally endoenergetic, so rises with increasing temperature, and the dissolution of Na2SO4 is globally exoenergetic so decreases with increasing temperature.

Am I right?

 

[Gokul43201]

Perfectly.

PS : Please do not help folks that show no original effort. It is rarely helpful to the student in the long run.