The question given below consist of an assertion and a reason. Use the following key to choose the appropriate answer.

(a) Both Assertion and reason are correct statements, and Reason is the correct explanation of assertion.

(b) Both Assertion and reason are correct statements, and Reason is not the correct explanation of assertion.

(c) Assertion is correct, Reason is the wrong statement.

(d) Assertion is wrong, but Reason is the correct statement.

Assertion: The solubility of a gas decreases with increase in temperature.

Reason: Dissolution of gas in a liquid is an endothermic process.

(c)

The solubility of a gas in a liquid refers to the amount of gas that can dissolve in a given amount of solvent at a particular temperature and pressure. The solubility of a gas in a liquid is affected by several factors, including temperature.

When it comes to the effect of temperature on gas solubility, the general trend is that the solubility of most gases decreases as the temperature increases. This phenomenon can be explained by considering the behavior of gas molecules and the principles of thermodynamics.

Gas molecules possess kinetic energy due to their constant random motion. The higher the temperature, the greater the average kinetic energy of the gas molecules. As a result, at higher temperatures, the gas molecules move more rapidly and have increased energy.

In the context of dissolving gas in a liquid, this increased kinetic energy has an impact. When a gas is in contact with a liquid, the gas molecules are in constant motion and collide with the liquid molecules. Some of these collisions result in gas molecules being captured by the liquid and dissolving.

The dissolution of a gas in a liquid is an exothermic or endothermic process, depending on the specific gas-liquid combination. However, the reason provided in the initial statement suggesting that the dissolution of gas in a liquid is an endothermic process is incorrect in the general sense.

In reality, the dissolution of most gases in liquids is an exothermic process, meaning it releases heat to the surroundings. When gas molecules are captured by the liquid and become solvated, they interact with the solvent molecules, which results in the formation of intermolecular attractions and a decrease in the potential energy of the system. This release of energy typically manifests as heat.

Now, let's focus on the effect of temperature. When the temperature of the system is increased, the average kinetic energy of the gas molecules also increases. As a result, the gas molecules move more vigorously and collide with the liquid molecules with greater force and frequency.

These energetic collisions can disrupt the intermolecular attractions between the gas molecules and the solvent molecules. Consequently, the solvated gas molecules may escape from the liquid phase and return to the gas phase. This process is known as desolvation or degassing.

Therefore, when the temperature of the system increases, the solubility of most gases in a liquid decreases because the rate of desolvation exceeds the rate of solvation. In other words, the gas molecules are more likely to escape from the liquid phase and return to the gas phase, reducing the overall solubility.

In summary, the solubility of a gas in a liquid generally decreases with an increase in temperature. This is because the increased kinetic energy at higher temperatures promotes the escape of gas molecules from the liquid phase, decreasing the solubility. The dissolution of most gases in liquids is an exothermic process, not an endothermic one.