Class 12 Chemistry - KERALA
Chemical Kinetics
Chemical Kinetics is a crucial branch of physical chemistry that deals with the rates of chemical reactions and the factors affecting them, such as concentration, temperature, and catalysts. For Kerala SCERT Class 12 board exams, this chapter is a high-scoring area that thoroughly tests your numerical problem-solving abilities and theoretical understanding. You will learn how to determine reaction rates, express rate laws, calculate order and molecularity of reactions, and apply the Arrhenius equation to understand temperature dependence. Mastering integrated rate equations for zero and first-order reactions is essential for scoring top marks.
Start Learning FreeKey Concepts
Rate of a Chemical Reaction
The change in concentration of a reactant or product in a given unit of time, expressed in units like mol L⁻¹ s⁻¹.
Rate Law and Rate Constant
Rate law expresses the reaction rate in terms of molar concentrations of reactants with each term raised to some power. The rate constant (k) is the proportionality factor in this equation.
Order and Molecularity
Order of a reaction is the sum of powers of concentration terms in the rate law (can be zero, fractional, or integer), whereas molecularity is the number of reacting species colliding simultaneously in an elementary step (always a whole number).
Integrated Rate Equations
Mathematical expressions that relate reactant concentration at any given time to the initial concentration and rate constant, specifically important for zero-order and first-order reactions.
Arrhenius Equation
An equation that quantitatively shows the dependence of the rate constant of a reaction on absolute temperature and activation energy.
Important Formulas
Board Exam Info
In the Kerala SCERT Class 12 Chemistry board exam, Chemical Kinetics typically carries around 5 to 7 marks. Questions frequently include numerical problems based on first-order half-life, graphical representations of zero and first-order reactions, derivations of integrated rate equations, and theoretical questions on activation energy and catalysts.
Frequently Asked Questions
What is the difference between order and molecularity?
Order is an experimentally determined quantity which can be zero, fractional, or integer and applies to overall reactions. Molecularity is a theoretical concept representing the number of molecules colliding in an elementary step and is always a positive integer (1, 2, or 3).
Can the order of a reaction be negative?
Yes, the order of a reaction with respect to a particular reactant can be negative if that reactant inhibits the reaction rate, though overall orders are usually positive or zero.
Why does the rate of a reaction generally increase with temperature?
Raising the temperature increases the kinetic energy of reactant molecules, leading to a greater number of effective collisions that possess energy equal to or greater than the activation energy.
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