Problem 13 - A Complete Resource Book in Chemistry for JEE Main

Question

The solubility of a gas in a liquid increases with (a) increase of temperature (b) amount of liquid taken (c) decrease in temperature (d) reduction of gas pressure

Step-by-Step Solution

Answer

(c) decrease in temperature

Step 1: Analyze Temperature Influence

Begin by understanding how temperature impacts the solubility of gases in liquids. Generally, solubility of gases in liquids decreases with an increase in temperature. Hence, a decrease in temperature increases gas solubility.

Step 2: Assess Impact of Additional Liquid

Evaluate if adding more liquid affects solubility. The solubility of a gas is independent of the amount of liquid as it is expressed in terms of concentration, typically per unit volume.

Step 3: Understand Gas Pressure Effect

Consider how gas pressure influences solubility. According to Henry's Law, solubility of a gas in a liquid is directly proportional to the pressure of that gas above the liquid. Thus, a reduction in gas pressure decreases solubility.

Step 4: Conclusion

Based on the examination, decreased temperature (c) is the factor that increases the solubility of a gas in a liquid.

Key Concepts

Temperature Effect on Solubility

Understanding the temperature effect on gas solubility is crucial for applications involving gases dissolved in liquids, such as carbonated beverages. Typically, the solubility of gases in liquids decreases with an increase in temperature. This behavior is different from solutes like solids, where increasing temperature usually increases solubility.
For gases, higher temperatures provide particles with more kinetic energy. This extra energy allows gas molecules to escape more easily from the liquid phase into the gaseous phase. Conversely, at lower temperatures, gas molecules have less energy and tend to remain dissolved. Thus, to increase the solubility of a gas, you should lower the temperature of the solution.

Henry's Law

Henry's Law is a pivotal principle in understanding gas solubility, stating that the solubility of a gas in a liquid at a given temperature is directly proportional to the partial pressure of that gas above the liquid. This relationship can be expressed mathematically as:
\[ C = kP \]where:

• \( C \) is the solubility of the gas
• \( P \) represents the partial pressure of the gas
• \( k \) is Henry's Law constant, specific to each gas-liquid pair and temperature.

An increase in gas pressure above the liquid results in more gas molecules entering the solution until equilibrium is reached. Conversely, a decrease in pressure leads to gas molecules leaving the solution, reducing solubility.

Pressure and Solubility

The relationship between pressure and gas solubility is directly related to Henry's Law. When the pressure of a gas above a liquid is high, more gas molecules collide with the liquid's surface, making it more likely for them to dissolve.
This principle is commonly seen in sealed carbonated drinks. Upon opening, the pressure above the liquid decreases sharply, leading to gas escaping from the solution in the form of bubbles.
Therefore, to maintain increased solubility of gases, it is essential to maintain higher pressures. Conversely, reducing pressure will cause dissolved gas to be released, decreasing solubility.