📘 Understanding Henry’s Law Constant (KH) and Its Applications
Here’s a CBSE Class 12 board exam–oriented and classroom-friendly explanation of the above content from the NCERT Henry’s Law section, including the meaning of Henry’s constant (KH), the graph, and the effect of temperature — all simplified for better understanding:
📘 Understanding Henry’s Law Constant (KH) and Its Applications
🔬 What is KH?
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KH is the Henry’s Law constant.
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It tells us how easily a gas dissolves in a liquid under pressure.
📖 From Henry’s Law:
Where:
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p = partial pressure of the gas
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x = mole fraction (solubility) of the gas
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KH = constant (depends on gas and temperature)
📈 Graph Between p and x (Henry’s Law – Fig. 2.2)
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If you plot:
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Y-axis = partial pressure of gas (p)
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X-axis = mole fraction (x)
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You get a straight line, with slope = KH
📌 Higher slope = less solubility, because KH is higher.
📌 Interpretation of KH:
Higher the value of KH, the lower the solubility of the gas at a given pressure.
✅ So, gases with low KH values dissolve more easily.
❌ Gases with high KH values are less soluble.
🧪 Examples from Table 2.2:
| Gas | Temp (K) | KH (kbar) | Solubility Trend |
|---|---|---|---|
| CO₂ | 298 | 1.67 | Very high solubility |
| O₂ | 293 | 34.86 | Moderate |
| N₂ | 293 | 76.48 | Low |
| He | 293 | 144.97 | Very low |
| Methane | 298 | 0.413 | High solubility |
🌡️ Effect of Temperature on KH:
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KH increases with temperature
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So, gas solubility decreases as temperature increases
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That’s why cold water holds more dissolved oxygen than warm water
🐟 Real-Life Example:
Aquatic animals live better in cold water because cold water dissolves more oxygen (lower KH).
📝 CBSE Exam Tips:
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Always mention that KH depends on the nature of gas and temperature
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State clearly:
Higher KH ⇒ lower solubility
Higher temperature ⇒ higher KH ⇒ lower solubility
Would you like me to prepare a clean classroom chart with this KH table, graph, and summary points for display or slides?
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