Surface Chemistry – Class 12 Chemistry Notes | Full NCERT Summary
🔬 Chapter 5: Surface Chemistry – Class 12 Chemistry
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🔹 What is Surface Chemistry?
Deals with phenomena occurring at the interface between two phases: solid-liquid, solid-gas, or liquid-gas.
Important in adsorption, catalysis, and colloidal systems.
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🔹 Adsorption
Definition: Accumulation of molecules on the surface of a solid or liquid.
Types:
1. Physisorption – Weak Van der Waals forces, reversible.
2. Chemisorption – Strong chemical bonds, irreversible.
📌 Important Diagram: Graph between temperature and extent of adsorption
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🔹 Adsorption Isotherms
Freundlich Adsorption Isotherm:
x/m = kP^{1/n}
= mass of adsorbate
= mass of adsorbent
= pressure
📌 Diagram: Freundlich isotherm plot
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🔹 Catalysis
Catalyst: A substance that alters the rate of a reaction without being consumed.
Types of Catalysis:
1. Homogeneous Catalysis – Reactants and catalyst in the same phase.
2. Heterogeneous Catalysis – Catalyst in a different phase.
📌 Diagram: Energy profile diagram showing catalytic path
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🔹 Characteristics of Catalysis
Catalyst remains unchanged in mass and composition.
Specific in action.
Increases rate but does not change equilibrium.
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🔹 Colloids
A colloid is a heterogeneous system in which one substance is dispersed in another.
Types of Colloids:
Sol – Solid in liquid
Gel – Liquid in solid
Aerosol – Solid/liquid in gas
Emulsion – Liquid in liquid
📌 Diagram: Types of colloids with examples (chart)
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🔹 Properties of Colloids
Tyndall Effect – Scattering of light.
Brownian Movement – Zig-zag motion of particles.
Electrophoresis – Movement under electric field.
Coagulation – Precipitation of colloids by electrolytes.
📌 Diagram: Tyndall effect and Brownian motion setup
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🔹 Emulsions
Liquid in liquid colloidal systems.
Types:
Oil in water (milk)
Water in oil (butter)
Emulsifier: A substance that stabilizes an emulsion (e.g., soap).
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🔹 Cleaning Action of Soaps
Soap molecules have hydrophobic tail and hydrophilic head.
Form micelles in water to trap dirt and grease.
📌 Diagram: Structure of a micelle
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✅ Summary Table
Topic Key Points
Adsorption Surface accumulation
Catalysis Increases reaction rate
Colloids Dispersed phase in dispersion medium
Emulsions Liquid in liquid colloid
Micelles Soap molecules trapping grease
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🖼️ Important Diagrams to Include
1. Graph: Adsorption vs Temperature
2. Freundlich Isotherm Graph
3. Energy Profile of Catalyzed vs Uncatalyzed Reaction
4. Chart of Types of Colloids
5. Tyndall Effect S
etup
6. Brownian Motion Apparatus
7. Micelle Structure
8. Electrophoresis Setup
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✍️ Written by: Shahid – Study with Shahid
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