Question

Assertion: The molecules of the dissolved gas present in a liquid gain kinetic energy as the temperature is raised.
Reason: Gases tend to be more soluble in liquids as the temperature is raised.

Answer 1

First we need to understand what is kinetic energy. The energy possessed by an object which is in motion and has a certain amount of mass is known as its kinetic energy. It can also be defined as the force required or the work needed to be done to accelerate an object of a given mass.

Complete answer:
When there is an increase in temperature of a solution, the kinetic energy of the molecules of the gas dissolved in the liquid increases.
Due to this increase in kinetic energy, the motion of the gas molecules increases, and the intermolecular bonds between them break.
This causes the gas molecules to escape from the solution.
This is why when the temperature of a solution is raised, the solubility of gases decreases.
So the assertion that the molecules of the dissolved gas present in a liquid gain kinetic energy as the temperature is raised is correct but the reason given that gases tend to be more soluble in liquids as the temperature is raised is false.

Additional Information:
The dissolution of a gas in a liquid is also governed by Henry's Gas Law which states that the amount of gas dissolved in a liquid is proportional to its partial pressure above the liquid. Hence when the pressure increases, the solubility of a gas in a liquid also increases.
$C=k{{P}_{gas}}$
Where the solubility of the gas at a particular temperature in a given solute is denoted by C (unit: M). Henry's law constant is denoted by k (unit: M/atm) and the partial pressure of the gas is denoted by ${{P}_{gas}}$ (unit: atm).

Note:
It should be noted that the solubility of a gas in a liquid is an exothermic process. So, according to Le Chatelier's principle, when the temperature of an exothermic reaction is increased, the equilibrium will shift backward and hence there will be a decrease in solubility of the gas in the liquid.