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CBSE Class 12th Chemistry Notes for Chapter 4 Chemical Kinetics


  • Chemical kinetics is the study of chemical reactions with respect to reaction rates, effect of various variables, rearrangement of atoms and formation of intermediates.


  • The rate of reaction is concerned with decrease in concentration of reactants or increase in the concentration of products per unit time. It can be expressed as instantaneous rate at a particular instant of time and average rate over a large interval of time.


  • A number of factors such as temperature, concentration of reactants, catalyst, etc., affect the rate of a reaction.


  • Mathematical representation of the rate of a reaction is called the rate law.


  • Order of a reaction with respect to a reactant is the power of its concentration which appears in the rate law equation. The order of a reaction is the sum of all such powers of concentration of terms for different reactants.


  • Rate constant is the proportionality factor in the rate law or its integrated rate equation.


  • Molecularity is defined only for an elementary reaction. Its values are limited from 1 to 3 whereas order can be 0, 1, 2, 3 or even a fraction.


  • Temperature dependence of rate constants is described by Arrhenius equation.


  • Activation energy is given by the energy difference between activated complex and the reactant molecules.


  • According to collision theory, another factor called steric factor which refers to the orientation of molecules which collide, is important and contributes to effective collisions.

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