Question

What is the effect of temperature on solubility of $KN{{O}_{3}}\,\text{and }CaS{{O}_{4}}$ is water?

Answer 1

Hint: The energy released or absorbed while breaking old bonds in the solute and solvent molecules in order to form new bonds in the solution, between solute-solvent molecules which are affected by the varying temperature.
The solubility of the solution can be determined by considering the change caused due to temperature increase as it tries to get the system back in equilibrium state.

Complete step by step answer:
Both the potassium nitrate and calcium sulphate are solid compounds. The solubility of these compounds in water depends on their solvation enthalpy, that is, whether the reaction process is endothermic or exothermic using Le Chatelier’s principle.
So, under constant pressure, when the temperature is varied, the solubility of the solution varies as the system tries to attain back the equilibrium between the reactant and product side by countering the change as stated by Le Chatelier’s principle.
- In case of potassium nitrate solid dissolved in water, it is an endothermic reaction as it absorbs the heat during the reaction, then, $\Delta {{H}_{solvation}}>0$. On increasing the temperature, the reactant side with $KN{{O}_{3}}$solute molecules experience more energy. Thereby, shifting the reaction towards the reactant side. But in order to attain back the equilibrium, the system will shift towards the product side causing more solute molecules to dissociate in water. Thus, increasing the solubility.
- Whereas, in case of calcium sulphate, the reaction is exothermic as it releases heat, then$\Delta {{H}_{solvation}}<0$and on increasing the temperature the product side experience more energy shifting the reaction towards the product side. But through Le Chatelier’s principle, the system will shift towards the reactant side to attain back the equilibrium. Thus, causing less $CaS{{O}_{4}}$solute molecules to dissolve in water and decreasing the solubility.

Note: The solvation enthalpy $(\Delta {{H}_{solvation}})$of a solution is the amount of energy released or gained while dissolving the solute in the solvent. The intermolecular forces between the solute molecules and between the solvent molecules are broken with the release or gain of energy as they form a new bond between the solute-solvent molecules.