Home » CBSE Class 12th Chemistry Notes for Chapter 5 Surface Chemistry

CBSE Class 12th Chemistry Notes for Chapter 5 Surface Chemistry

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         UNIT 5 SURFACE CHEMISTRY
 

  • Adsorption is the phenomenon of attracting and retaining the molecules of a substance on the surface of a solid resulting into a higher concentration on the surface than in the bulk.

 

  • The substance that is adsorbed is called the adsorbate and the substance on which adsorption takes place is called the adsorbent.

 

  • Almost all solids adsorb gases. The extent of adsorption of a gas on a solid depends upon:
    • the nature of gas
    • the nature of the solid
    • surface area of the solid
    • pressure of gas
    • temperature of gas

 

  • The relationship between the extent of adsorption and the pressure of the gas at constant temperature is known as adsorption isotherm.

 

  • A catalyst is a substance which enhances the rate of a chemical reaction without itself getting used up in the reaction. The phenomenon using catalysis is known as catalysis.

 

  • Homogeneous catalysis: The catalyst is in the same phase as the reactants.

 

  • Heterogeneous catalysis: The catalyst is in a different phase from that of the reactants

 

  •  Colloidal solutions are intermediate between true solutions and suspensions. The size of colloidal particles range from 1 to 1000 nm.

 

  • A colloidal system consists of two phases: the dispersed phase and the dispersion medium.

 

  • Colloidal system can be classified in three ways depending upon the:
    • Physical states of the dispersed phase and the dispersion medium
    • Nature of interaction between the dispersed phase and the dispersion medium
    • Nature of particles of dispersed phase
    • The process of changing the colloidal particles in a sol into the insoluble precipitate by addition of some suitable electrolytes is known as coagulation.
    • Emulsions are colloidal systems in which both the dispersed phase and dispersion medium are liquids. The process of making emulsions is called emulsification.

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