solubility 4

 Certainly, Mayank! Here's a CBSE Class 12-friendly, exam-oriented, and impactful explanation of Solubility, designed for smart board/lecture slides or student notes. It’s clear, to the point, and aligned with the CBSE NCERT format.

🌊 Solubility – Class 12 (CBSE Focus)

🔍 Definition (For Board Exams)

Solubility of a substance is the maximum amount of solute that can be dissolved in a specified amount of solvent at a given temperature and pressure to form a saturated solution.

✍️ Write this definition exactly as it is in NCERT for exams.

✅ Key Concepts (Keep it Student-Friendly)

🧪 Solute = the substance that dissolves
💧 Solvent = the substance in which solute dissolves
🧫 Saturated solution = no more solute can dissolve at given T and P
🔁 Dynamic equilibrium:

Dissolution rate = Crystallisation rate

🎯 Factors Affecting Solubility

(📝 All these are important for CBSE exams)

1. 🔄 Nature of Solute and Solvent

📌 Rule: "Like dissolves like"

Type Example Solubility
Polar in polar NaCl in water ✅ Dissolves
Non-polar in non-polar Naphthalene in benzene ✅ Dissolves
Polar in non-polar Sugar in benzene ❌ Does not dissolve

2. 🌡️ Effect of Temperature

🧪 For solids in liquids:

  • If endothermic (∆H > 0): Solubility ↑ with temperature

  • If exothermic (∆H < 0): Solubility ↓ with temperature
    📌 Use Le Chatelier’s Principle

🧪 For gases in liquids:

  • Solubility decreases with rise in temperature
    📌 Gas escapes more at higher temperature

3. 🧯 Effect of Pressure (Only for Gases)

✔️ For gases, solubility increases with increase in pressure

📘 Henry’s Law (CBSE Must-Know)

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

📌 Formula:

p=KH×xp = K_H \times x

Where:

  • p = partial pressure of gas

  • x = mole fraction of gas in solution

  • KH = Henry’s constant

🔺 Higher KH ⇒ Lower solubility

🔬 Applications of Henry’s Law (Short Notes)

Application Explanation
Soft drinks CO₂ dissolved at high pressure
Scuba diving High pressure dissolves more gases → risk of nitrogen bubbles (bends)
Mountains Low oxygen pressure → less O₂ dissolves in blood → anoxia (breathlessness)

📊 Important KH Values (Ask in MCQs)

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

🧠 Tips for Exams:

✔ Write definitions exactly as in NCERT
✔ Use diagrams if asked (dynamic equilibrium, Henry’s law graph)
✔ Always mention Le Chatelier’s Principle when explaining temperature effects
✔ Learn 3 uses of Henry’s Law (1 line each – scoring)

📝 Sample Board Question:

Q. Define solubility. What are the factors affecting solubility of a solid and a gas in liquid?
🟩 Write definition + nature + temperature + pressure points.

Would you like a PDF version, PowerPoint slides, or a printable notes page for your classroom or website?

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