💨 Effect of Pressure on Solubility of Gases in Liquids

 Here’s a CBSE Class 12–oriented explanation of the paragraph you provided, presented in a student-friendly, simplified format—perfect for classroom teaching, notes, or slides.

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💨 Effect of Pressure on Solubility of Gases in Liquids

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✅ Key Concept:

Solubility of a gas in a liquid increases with increase in pressure.

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🔬 How Does It Work?

• Consider a container with gas above a liquid at pressure p and temperature T.

• Gas molecules are constantly moving — some enter the liquid (dissolution), while others leave (escape).

📌 At dynamic equilibrium, the rate of gas entering = rate of gas leaving the solution.

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🔺 Now Increase the Pressure:

• By compressing the gas, we increase the number of gas particles per unit volume.

• More gas molecules hit the liquid surface → more gas dissolves into the liquid.

• A new equilibrium is established, but now with higher gas solubility.

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⚖️ Henry’s Law – Explains the Relationship

At constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.

🧪 Mathematical Form:

$$p = K_H \cdot x$$

Where:

• p = partial pressure of the gas above the solution

• x = mole fraction of gas in the solution

• KH = Henry’s law constant (depends on the gas and temperature)

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📈 Graph:

A straight-line graph is obtained when we plot:

• p (y-axis) vs x (x-axis)
  ➝ Slope = KH

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📌 Important Observations:

• Different gases have different KH values.

• Higher KH = Lower solubility of gas.

• KH increases with temperature, so solubility of gas decreases as temperature rises.

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📝 Example (from Table):

Gas	Temp (K)	KH (kbar)	Solubility
CO₂	298	1.67	High
O₂	293	34.86	Moderate
N₂	293	76.48	Low
He	293	144.97	Very Low

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🧠 Summary:

Factor	Effect on Gas Solubility
↑ Pressure	↑ Solubility
↑ Temperature	↓ Solubility
↑ KH value	↓ Solubility

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✅ CBSE Exam Tip:

• Always define Henry’s Law clearly and write the formula:

  $$p = K_H \cdot x$$

• Mention dynamic equilibrium, molecular collisions, and applications.

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