Class 12 Chemistry - TAMILNADU
Chemical Kinetics
Chemical Kinetics is a crucial chapter in the Class 12 Tamil Nadu Samacheer Kalvi Chemistry syllabus that explores the speed or rate of chemical reactions and the factors affecting them. It bridges thermodynamics and quantum chemistry by determining not just if a reaction is feasible, but how fast it proceeds. You will study reaction rates, rate laws, molecularity, order of reactions, integrated rate equations for zero and first-order reactions, and the Arrhenius equation. Mastering this chapter is essential for scoring high marks in your board exams, as it features a mix of conceptual reasoning questions and important numerical problems.
Start Learning FreeKey Concepts
Rate of a Reaction
The change in concentration of a reactant or product per unit time, expressed in units like mol L^-1 s^-1.
Rate Law and Rate Constant
An expression that relates the rate of a reaction to the concentrations of reactants with each term raised to some power, where the proportionality constant is the rate constant (k).
Order of a Reaction
The sum of the powers of the concentration terms of the reactants in the rate law expression, which can be zero, fractional, or integer.
Molecularity
The total number of reacting species colliding simultaneously in an elementary reaction; it is always a whole number and cannot be zero or fractional.
Arrhenius Equation
An equation that expresses the quantitative relationship between the rate constant and temperature, highlighting the concept of activation energy.
Important Formulas
Board Exam Info
In the Tamil Nadu (Samacheer Kalvi) Class 12 Chemistry board exam, Chemical Kinetics typically carries around 5 to 7 marks. Questions frequently include direct definitions, derivations of half-life or integrated rate equations for first-order reactions, graphical questions, and numerical problems based on the Arrhenius equation and rate constants.
Frequently Asked Questions
What is the difference between order and molecularity of a reaction?
Order is an experimentally determined quantity that can be zero, fractional, or integer, based on the rate law. Molecularity is a theoretical concept representing the number of reacting species in an elementary step and is always a positive whole number.
Can the order of a reaction be negative?
Yes, in complex reactions, the rate may decrease with an increase in the concentration of certain intermediates or products, resulting in a negative reaction order.
Why does the rate of a reaction generally increase with temperature?
Higher temperature increases the kinetic energy of reactant molecules, leading to a greater number of effective collisions that overcome the activation energy barrier.
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