# Chemical Kinetics Notes, Class 12 Chemistry | SwaVid Chemical Kinetics, NCERT Class 12 Chemistry: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-12/chemistry/chapter/chemical-kinetics Source: https://www.swavid.com/cbse/class-12/chemistry/chapter/chemical-kinetics # Chemical Kinetics ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 12 Chemistry on SwaVid ### Rate of a chemical reaction ### Rate law and order of reaction ### Molecularity of a reaction ### Integrated rate equations ### Half-life of a reaction ### Temperature dependence and Arrhenius equation ### Collision theory of chemical reactions ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 12 › Chemistry › Chemical Kinetics Notes written by SwaVid from the NCERT textbook. Class 12 Chemistry, Unit 3. Key ideas, formulas and common mistakes. CBSE prints 7 marks for Unit 3, not for this chapter alone. Short answer. This chapter deals with the speeds of chemical reactions and the factors that influence them. Students learn how to write rate laws, determine reaction orders, and calculate rate constants using integrated equations and temperature dependence. Source: NCERT Chemistry Part I (Reprint 2026-27) , Unit 3, Chemical Kinetics The rate of a reaction is the change in concentration of a reactant or product per unit time. Average rate is measured over a finite time interval, while instantaneous rate is the rate at a specific moment represented by a derivative. A rate law expresses the reaction rate in terms of molar concentrations of reactants raised to powers determined by experiment. The sum of these powers gives the overall order of the reaction, which can be zero, fractional, or an integer. Molecularity is the number of reacting species taking part in an elementary step that collide simultaneously to cause a chemical change. Unlike order, molecularity is always a positive integer and cannot be zero or fractional. Integrated rate laws link reactant concentration directly with time. For a zero-order reaction, concentration decreases linearly with time, whereas for a first-order reaction, the logarithm of concentration decreases linearly with time. The half-life is the time required for the reactant concentration to decrease to half of its initial value. The half-life of a first-order reaction is independent of the initial concentration, while for a zero-order reaction it is directly proportional to it. The rate constant increases exponentially with an increase in temperature. The Arrhenius equation links the rate constant to absolute temperature and activation energy, which is the minimum energy required to form an activated complex. Reactions occur when reactant molecules collide with sufficient kinetic energy and proper steric orientation. Collisions that meet both the activation energy threshold and orientation criteria are called effective collisions. Try each question first. Then tap it to see the answer. t₁/₂ = 0.693 / k t₁/₂ = 0.693 / (2.31 × 10⁻³ s⁻¹) t₁/₂ = 300 s 300 s Unit of k is (mol L⁻¹)^(1 - n) s⁻¹ = mol^(1 - n) L^(n - 1) s⁻¹ Comparing power of L: n - 1 = 1 n = 2 Second order Let [R]₀ = 100, then [R] = 100 - 30 = 70 k = (2.303 / 40 min) × log₁₀ (100 / 70) k = (2.303 / 40 min) × 0.1549 k = 8.92 × 10⁻³ min⁻¹ 8.92 × 10⁻³ min⁻¹ The d- and f-Block Elements . Solutions . Electrochemistry . The 10 chapters of Class 12 Chemistry . CBSE does not give marks to one chapter. It prints 7 marks for Unit 3, Chemical Kinetics, which includes Chemical Kinetics. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. The d- and f-Block Elements. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Unit 3 NCERT book - 7 marks, Unit 3 - 3 quick checks - Writing the rate law directly from stoichiometric coefficients of a balanced equation . Order and rate laws are purely experimental properties. Stoichiometric coefficients can only be used as powers if the reaction is explicitly stated to be an elementary step. - Using mol L⁻¹ s⁻¹ as the unit of rate constant for all reaction orders . Only the reaction rate has fixed units of mol L⁻¹ s⁻¹; the unit of the rate constant k varies with the overall order n and is given by (mol L⁻¹)^(1 - n) s⁻¹. - Assuming molecularity applies to complex reactions . Molecularity is meaningful only for elementary reactions. For a complex multi-step reaction, molecularity has no overall meaning, though each individual step has its own molecularity. - Using temperature in Celsius inside the Arrhenius equation . 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