Question

In an endothermic process, solubility increases with ______ in temperature.
(A) increase
(B) decrease
(C) remains same
(D) none of the above

Answer 1

Hint: Solubility depends upon the temperature and pressure variations during the process. It varies with respect to exothermic and endothermic reactions. In the endothermic process, heat is absorbed.

Complete step by step solution:
Before considering some cases let us priorly understand what we mean by solubility;
Solubility- The maximum quantity of solute that can dissolve in a certain quantity of solvent or quantity of solution at a specified temperature and pressure is known as solubility.
In reality, almost every solute is somewhat soluble in every solvent at some measurable extent.
Temperature and pressure play a major role in determining the degree to which solute is soluble.
We will here concentrate on cases which vary with respect to temperature.
For gases-
Solubility decreases as temperature increases. The physical reason for this is that when most gases dissolve in solution, the process is exothermic which means that heat is released as gas dissolves.
For solid and liquid solutes-
Case 1 (Decrease in solubility with temperature)-
If the heat is given off in the dissolving process is greater than the heat required to break apart the solid, the net dissolving reaction is exothermic. The addition of more heat inhibits the dissolving reaction. This situation is not very common but this is the case with sodium sulphate and calcium hydroxide.
Case 2 (Increase in solubility with temperature)-
If the heat given off in the dissolving process is less than the heat required to break apart the solid, the net dissolving reaction is endothermic. The addition of more heat facilitates the dissolving reaction. This is the most common situation.
The effect of temperature on solubility can be explained on the basis of Le Chatelier’s Principle.
Dissolution is an endothermic process. For many solids that dissolve in liquid, the solubility increases with the increase in temperature. Increase in temperature increases kinetic energy that comes with higher temperature allowing the solvent molecules to more efficiently break apart the solute molecules that are held by strong intermolecular attraction.

If we increase temperature, temporarily the rate of dissolution of solute increases and solute dissolves in solvent but when the temperature decreases automatically the excess amount of solute remains undissolved in solvent.
Therefore, in endothermic reactions, increasing the temperature increases the solubility of solute in a solution.

Thus, option (A) increase is the correct option.

Note: Do note that there are cases where solubility shows constant but indifferent behaviour with respect to temperature. But, the most common one should be remembered i.e. solubility increases with increase in temperature.