⚖️ Henry’s Law – Explained

 Here’s a simple, CBSE Class 12–friendly explanation of the paragraph you've shared about Henry’s Law, including the meaning, mathematical form, and graph — perfect for board exams and classroom presentations.

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⚖️ Henry’s Law – Explained

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📖 What is Henry’s Law?

Henry’s Law gives a quantitative relationship between the pressure of a gas and its solubility in a liquid.

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🔬 Statement of Henry’s Law:

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

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🧪 Mathematical Expression:

$$p = K_H \cdot x$$

Where:

• p = partial pressure of the gas (in vapour phase)

• x = mole fraction of the gas in solution

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

📌 This is the most commonly used form of Henry's law in Class 12.

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📈 Graphical Representation (Fig. 2.2):

• When we plot partial pressure (p) on the y-axis and mole fraction (x) on the x-axis, we get a straight line.

• The slope of this line = KH

• This graph shows that as pressure increases, mole fraction (i.e., solubility) increases.

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📌 Key Points to Remember:

• Higher pressure ⇒ More gas dissolves in liquid

• Higher value of KH ⇒ Lower solubility
  (Because the same pressure gives less mole fraction)

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🧠 Historical Note (CBSE extra info):

• William Henry first proposed this law in 1803.

• Dalton, a contemporary scientist, also found similar results — he stated that gas solubility depends on partial pressure.

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✅ CBSE Exam Tip:

• Write the statement + formula of Henry’s Law.

• Explain what each symbol means.

• Mention the graph (p vs x) is a straight line.

• Remember: "More pressure = More solubility" — direct proportionality.

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Would you like a clean visual of Fig. 2.2, or a ready-to-use slide that includes this law and its graph for class?