Chemical Kinetics Notes :

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Chemical kinetics is the study of the rates of chemical reactions. In order to understand how fast a reaction will occur, we need to know the rate law. The rate law tells us how the rate of a reaction depends on the concentrations of the reactants. For example, if the rate law is first order, then the rate of the reaction will be proportional to the concentration of one of the reactants.

If the rate law is second order, then the rate of the reaction will be proportional to the square of the concentration of one of the reactants. We can use this information to determine how changing the concentrations of reactants will affect the rate of a reaction. In this chemical kinetics notes you will get all the topics covered.

Understanding Reaction Rates and Mechanisms

Chemical kinetics, a crucial branch of chemistry, delves into the exploration of reaction rates, the factors influencing them, and the intricate mechanisms guiding chemical reactions. In Class 12 Chemistry, students embark on a journey to comprehend the dynamics of reactions, their speed, and the underlying principles that govern them. Here, we delve into the key aspects of Chemical Kinetics to aid in a comprehensive understanding.

Introduction to Chemical Kinetics

Chemical kinetics is the study of how fast or slow chemical reactions occur, the factors impacting their rates, and the intricate mechanisms governing these reactions. One fundamental concept is the rate of reaction, denoted by the change in concentration of reactants or products per unit time.

Rate of Reaction

The rate of reaction is not constant, except for zero-order reactions. It signifies the decrease in concentration with time and is measured in mol L⁻¹s⁻¹.

Rate Law

A rate law establishes a mathematical relationship between the rate of reaction and the molar concentration of reactants.

Rate Constant

The rate constant, denoted by ‘k,’ represents the rate of reaction when the concentration of each reacting species is unity. Also known as the specific reaction rate or velocity constant, it is a crucial parameter in understanding reaction kinetics.

Order of Reaction

The order of reaction is the sum of the exponents in the rate law equation, denoted as \(m + n\). It can be fractional, zero, or any whole number and is a key factor in determining the reaction kinetics.

Types of Reactions

– First Order Reaction: The reaction rate is determined by the variation of one concentration term only.

– Second Order Reaction: The sum of powers of concentration terms in the rate law equation is two.

– Zero Order Reaction: The rate of reaction remains constant regardless of the concentration of reactants.

Half-Life Period

The half-life period is the time required for the initial concentration of the reactant to reduce to half its value. It is a vital parameter in understanding the dynamics of reactions over time.

Temperature Dependence

The rate of reaction exhibits a strong dependency on temperature. For many reactions, a rise in temperature results in a nearly doubled rate constant.


Understanding chemical kinetics is crucial for predicting and controlling reactions in various fields. The concepts of rate, rate laws, order of reaction, and temperature dependence are indispensable tools in unraveling the mysteries of chemical reactions. As Class 12 students delve into the intricacies of Chemical Kinetics, these notes serve as a valuable guide to enhance their comprehension of reaction dynamics and mechanisms.

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