Question
Why do gases always tend to be less soluble in liquids as the temperature is raised?
Solution
Answer:
When gas dissolve in liquid it generate a small quantity of heat so we can say that dissolution of gas in a liquid is a exothermic reaction.
Gas + liquid < --- > solution + heat
According to le Chatelier's principle when we increase the temperature in a exothermic reaction , the reaction will move to back ward direction that means solution will dissociate and will give gas .Hence with the rise of temperature gas will less soluble.
For most of gases like N2, O2, He etc. the value of Henry's constant, KH increases with temperature and as a result of this solubility of gases decreases with increase of temperature. We know, at given temperature.
Partial pressure of gas in solution = KH x mole fraction of gas in sol. KH depends on the nature of gas. For example, KH value of O2 at 293 K is 34.86 while at 393 K it is 46.82 kilo bar.
