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Chapter Analysis
Advanced24 pages • EnglishQuick Summary
Chapter 3 of Class 12 Chemistry Part 1 focuses on 'Chemical Kinetics,' exploring the rate of chemical reactions and the factors influencing them. It differentiates between average and instantaneous rates, and introduces the rate law, which relates reaction rates to reactant concentrations. Major topics include zero and first order reactions, rate constants, and the collision theory. Factors such as concentration, temperature, and catalysts are discussed in relation to their effect on reaction rates.
Key Topics
- •Rate of reaction and factors affecting it
- •Order and molecularity of reactions
- •Rate laws and rate constant
- •Zero and first order reactions
- •Half-life of reactions
- •Collision theory
- •Effect of temperature on reaction rates
- •Role of catalysts
Learning Objectives
- ✓Define average and instantaneous rates of reactions
- ✓Express reaction rates in terms of reactant/product concentration changes
- ✓Distinguish between elementary and complex reactions
- ✓Differentiate between molecularity and order of a reaction
- ✓Define rate constant and its units for reactions of different orders
- ✓Understand the effects of concentration, temperature, and catalysts on reaction rates
Questions in Chapter
For a reaction, A + B → Product; the rate law is given by, r = k [A]1/2 [B]2. What is the order of the reaction?
Page 71
The conversion of molecules X to Y follows second order kinetics. If the concentration of X is increased to three times, how will it affect the rate of formation of Y?
Page 71
What will be the effect of temperature on rate constant?
Page 84
The rate of the chemical reaction doubles for an increase of 10K in absolute temperature from 298K. Calculate Ea.
Page 84
The activation energy for the reaction 2 HI(g) → H2 + I2 (g) is 209.5 kJ mol–1 at 581K. Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?
Page 84
Additional Practice Questions
Explain the difference between molecularity and order of reaction.
mediumAnswer: Molecularity refers to the number of molecules that participate in an elementary step of a reaction and is always a whole number, whereas the order of reaction is an experimentally determined value that shows the relation of reactant concentrations to the rate of reaction and can be zero or a fraction.
Describe the impact of a catalyst on the activation energy of a reaction.
easyAnswer: A catalyst provides an alternative reaction pathway with lower activation energy, increasing the rate of reaction without being consumed by the reaction itself.
What is the integrated rate equation for a first order reaction?
hardAnswer: The integrated rate equation for a first order reaction is ln[R] = -kt + ln[R]0, where [R] is the concentration of the reactant at time t, [R]0 is the initial concentration, k is the rate constant, and t is time.
How is the half-life of a zero order reaction different from that of a first order reaction?
mediumAnswer: The half-life of a zero order reaction is directly proportional to its initial concentration, whereas the half-life of a first order reaction is constant and independent of initial concentration.
Calculate the rate of a reaction when the concentrations of reactants and products are given.
mediumAnswer: To calculate the rate, use the rate law: Rate = k[A]x[B]y, where [A] and [B] are concentrations, x and y are their orders, and k is the rate constant.