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Chemical Kinetics
Chemical kinetics studies how fast a chemical reaction occurs and which factors control that speed. In Class 12 Chemistry, this chapter connects concentration changes, time, temperature, catalysts, and reaction mechanism with measurable reaction rates. The chapter is important for numerical questions because rate expressions, integrated rate equations, half-life relations, and Arrhenius calculations require correct formula selection, units, substitution, and interpretation. A reaction may be fast or slow depending on concentration, temperature, surface area, and catalyst. Chemical kinetics does not only ask what products form; it asks how quickly reactants are converted into products and what pathway the reaction may follow. CBSE questions commonly test rate law, order, molecularity, graphical identification of order, half-life, activation energy, and the role of catalysts using numerical data, short reasoning, assertion-reason, and graph-based interpretation.
Difficulty
Medium
Study time
70-90 min
Plan by time
Pick the window that matches what you have right now.
If you have 15 min
Last-pass revision
Skim the Quick Revision table — definitions, formulas, and the traps board examiners reuse.
Open Quick RevisionIf you have 45 min
Targeted practice
Read the high-priority concepts, then take the chapter MCQ quiz to find weak spots.
Start MCQ QuizIf you have 70 min
First full pass
Walk every concept in chapter order, then revise and quiz. Best for the first time you study this chapter.
Open Key ConceptsChapter Learning Map
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Key Concepts
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Core Concepts
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Rate of Reaction
Rate of reaction is the change in concentration of a reactant or product per unit time. For a reactant it is written with a negative sign because its concentration decreases, while for a product it is written with a positive sign because its concentration increases.
Rate Law, Order and Molecularity
Rate law expresses reaction rate in terms of molar concentrations of reactants raised to experimentally determined powers. Order is the sum of these powers. Molecularity is the number of reacting species taking part in a single elementary step.
Zero, First and Second Order Reactions
Zero, first, and second order reactions are classified by how rate depends on reactant concentration. Their integrated rate equations relate concentration and time, allowing calculation of rate constant, concentration remaining, or half-life.
Arrhenius Equation
The Arrhenius equation relates the rate constant of a reaction to temperature and activation energy: k = Ae^(-Ea/RT), where A is the frequency factor, Ea is activation energy, R is the gas constant, and T is absolute temperature.
Effect of Catalyst
A catalyst increases reaction rate by providing an alternate pathway with lower activation energy. It does not change the overall enthalpy change of the reaction and is regenerated by the end of the reaction.
Exam Intelligence
Use this section to decide what deserves the most revision time.
High Probability Topics
- Rate of Reaction
- Rate Law, Order and Molecularity
- Zero, First and Second Order Reactions
- Arrhenius Equation
- Effect of Catalyst
Common Traps
- Ignoring stoichiometric coefficients while writing rate expressions.
- Using balanced equation coefficients as rate law powers for overall reactions.
- Applying first order half-life formula to zero or second order reactions.
- Mixing seconds and minutes in k calculations.
- Using Celsius instead of kelvin in Arrhenius equation.
- Forgetting the negative sign in the Arrhenius plot slope.
- Claiming that a catalyst changes Delta H or equilibrium constant.
Likely Question Types
- MCQ: concept checks, applications, and common mistakes
- Very short answer: definitions, formulas, conditions, or terms
- Short answer: process, diagram, reasoning, or worked method
- Case-based: chapter scenario with linked subparts
Quick Revision
Concept, formula or equation to remember, and the trap that loses marks — in one scannable view.
- Reaction rate measures concentration change per unit time and must be corrected using stoichiometric coefficients.
- Rate law is experimental; order may be zero, fractional, or integral, while molecularity is only for elementary steps and is a whole number.
- Zero, first, and second order reactions have different integrated equations, graphs, half-life relations, and units of k.
- Arrhenius equation explains temperature dependence of rate constant through activation energy.
- Catalysts provide an alternate lower-energy pathway, increase rate, and leave Delta H and equilibrium constant unchanged.
- Rate of Reaction: Rate of reaction is the change in concentration of a reactant or product per unit time. For a reactant it is written with a negative sign b…
- Rate Law, Order and Molecularity: Rate law expresses reaction rate in terms of molar concentrations of reactants raised to experimentally determined powers. Order is the sum…
- Zero, First and Second Order Reactions: Zero, first, and second order reactions are classified by how rate depends on reactant concentration. Their integrated rate equations relat…
Practice
Use short concept checks first, then move into the full chapter test.
Free Chapter MCQ Quiz
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