Solubility of gas decreases in a liquid by

Options

A. Increase of temperature
B. Cooling
C. Increasing pH
D. Decreasing pH

Answer

To solve the question regarding how the solubility of a gas decreases in a liquid, we can break down the reasoning step by step.

### Step-by-Step Solution:

1. **Understanding Gas Solubility**: The solubility of a gas in a liquid is influenced by various factors, including temperature, pressure, and the nature of the gas and solvent.

2. **Effect of Temperature**: When the temperature of a liquid increases, the kinetic energy of the molecules in the liquid also increases. This increased kinetic energy causes gas molecules to escape from the liquid more readily.

3. **Entropy Consideration**: The dissolution of a gas in a liquid typically leads to a decrease in entropy because gas molecules have higher entropy in the gaseous state compared to when they are dissolved in a liquid. As temperature increases, the system tends to favor the gaseous state due to the higher entropy associated with it.

4. **Gibbs Free Energy**: The Gibbs free energy change (ΔG) for the dissolution process can be expressed as:
\[ \Delta G = \Delta H - T \Delta S \]
Where ΔH is the change in enthalpy, T is the temperature, and ΔS is the change in entropy. As temperature increases, the term \(T \Delta S\) becomes more significant, especially if ΔS is negative (which it is for gas dissolution). This can lead to a more negative ΔG, indicating that the dissolution process is less favorable.

5. **Conclusion**: Therefore, when the temperature of the liquid increases, the solubility of the gas decreases. This is because the gas is more likely to escape back into the gaseous phase, reducing its concentration in the liquid.

### Final Answer:
The solubility of gas decreases in a liquid by **increasing temperature** (Option A).

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