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# Xam Idea Class 12 Chemistry Chapter 4 Solutions: Chemical Kinetics

Xam Idea Class 12 Chemistry Solutions Chapter 4 – Chemical Kinetics is strictly based on the syllabus guidelines of CBSE and NCERT. Our Xam Idea solutions have been prepared by a team of expert Chemistry teachers. This chapter is based on a physical chemistry topic and needs you to understand the concepts well and remember the formulas to answer the questions from this topic. Our solutions are the best study material to refer to for scoring high in your Class 12 Chemistry Board Exams.

Part A of Xam Idea Class 12 Chemistry Solutions Chapter 4 contains all the chapter concepts and a variety of questions.  Some question types covered in this part include very short answer questions, short answer type questions and long answer type questions. Some questions are based on memory skills and higher-order thinking skills. Part B of our solution contains detailed solutions of sample questions papers based on the latest CBSE exam format.

This chapter tells you about average and instantaneous rates of reaction, expression of the reaction rates in terms of concentration change of the reactants and products, order and molecularity of reaction, the dependence of the rate of reaction on factors like catalyst, temperature and concentration. This chapter also tells you how to define and determine rate constant and what is collision theory.

## Xam Idea Class 12 Chemistry Chapter 4 – Chemical Kinetics

The chapter Chemical kinetics is a very important chapter in Class 12 Chemistry Syllabus. It fills the gap between theoretical predictions and the feasibility of chemical reactions. Our solutions include all the concepts of this chapter. They help you attain profound knowledge of the subject matter. The major components of this chapter are discussed below.

• Rate of a Chemical Reaction

This portion of the chapter tells you about the rate of any reaction. Measurement of a decrease in the number of reactants or increase in the number of products per unit time is known as the rate of reaction. This section also covers the overall reaction time, whereas the instantaneous rate is expressed at a time point, and the average rate of reaction is calculated for the whole duration of a reaction. General unit of rate of reaction is concentration/time. Our Xam Idea Class 12 Chemistry Solutions Chapter 4 – Chemical Kinetics are explained in a simple language which can easily be understood by you.

• Factors Influencing Rate of Reaction

In this portion of the chapter, you come to know that the rate of any reaction can be altered by several experimental conditions like the concentration of reactants, temperature, pressure in case of gases, presence of a catalyst. Further, you learn about rate law here where the reaction rate is expressed in terms of the molar concentration of reactants. Each of the reactant terms is raised to some power that may or may not be equal to the stoichiometric coefficient of the reactants in the balanced chemical equation.

• Order and molecularity of a reaction

This part of the chapter tells you that, Rate = k [A]x [B]y for a given rate equation. The sum of the exponents that is x + y tells the overall order of the reaction and x and y to represent the order of reactants A and B respectively. Further, you come to know that the unit of zero-order reaction is mol L-1 s-1, the first-order reaction is s-1 and the second-order reaction is mol-1 L s-1.

This part of the chapter lets you know that the number of ions, atoms or molecules reacting in elementary reaction to bring about the chemical reaction while colliding with each other, is known as molecularity of the elementary reaction. Its values are limited from 1 to 3 whereas order can be 0, 1, 2, 3 or even a fraction. Xam Idea Class 12 Chemistry Solutions Chapter 4 – Chemical Kinetics help you to solve all the questions related to this concept accurately.

• Integrated Rate Equations

This part teaches you that integration of differential equations of instantaneous rates give a relation between concentrations (of reactants or products) at different times and rate constant. Here you will learn that reactions having different reaction orders will have different integrated rate equations. For zero-order reaction, Rate = k and plot of concentration of reactant versus time can be plotted where the slope of the straight line obtained is equal to –k.

This section also tells you that in the case of first-order reactions rate equation is given as k = (2.303/t) log{[R]0/[R]}. When we plot ln[R] against t (time), we get a straight line with slope = –k and when we plot a graph between log[R]/[R]0 versus t the slope is given by k/2.303. A lot of numerical questions are asked in exams from these graphs. Xam Idea Class 12 Chemistry Solutions Chapter 4 – Chemical Kinetics provide excellent tips and techniques to solve numerical questions based on these concepts.

Further, you come to know that half-life of a reaction is the time in which the quantity of reacting species reduces to half of the initial quantity. Half-life is expressed as t1/2 = 0.693/k. For zero-order reactions, t1/2 is directly proportional to the initial concentration of reactant {[R]0}, and for the first-order reaction, t1/2 does not depend on [R]0.

• Pseudo First Order Reactions

This part of the chapter tells you that when one of the participating reactants is in large excess, for example when the reaction solvent is one of the reactants, it virtually does not affect the rate of reaction. This type of reaction is known as a pseudo-first-order reaction. Our smart, systematic and strategic Xam Idea Class 12 Chemistry Solutions Chapter 4 – Chemical Kinetics is the best study material to score good marks in class 12 board exams.

• Temperature dependence of the Rate of a Reaction

This part of the chapter deals with the dependence of a reaction on temperature. Here you learn that most of the chemical reactions occur in a fast manner when the reaction temperature is increased. Experimentally it has been found that the rate constant is nearly doubled when the reaction temperature is increased by 10 °C. Here you will also learn that the exact explanation of temperature dependence of reaction rate is given by Arrhenius equation, k = A e -Ea/RT, where A is Arrhenius factor, Ea is the activation energy. Increasing the temperature of the reaction system increases the fraction of molecules colliding with energies greater than Ea, finally giving rise to products.

This part further discusses the effect of a catalyst on a reaction. A catalyst is a substance which itself does not take part in the reaction but reduces activation energy to provide an alternate reaction mechanism.

• Collision Theory of Chemical Reactions

This portion of the chapter discusses the physical aspect of chemical reactions which is based on the actual collision of reacting molecules with each other. You come to know here that, according to collision theory steric factor, P, is important and contributes to the effective collisions. Prefers to the orientation of molecules which collide to give successful reactions. It modifies the Arrhenius equation as follows –k = PZAB e -Ea/RT.  Our Xam Idea Class 12 Chemistry Solutions Chapter 4 – Chemical Kinetics explains this concept beautifully.

### Xam Idea Class 12 Chemistry Chapter 4 – Exercises

Once you have learnt all the concepts, you need to practice the questions asked in this chapter of Xam Idea Class 12 Chemistry Book. The different types of questions covered here are very short answer questions and long answer questions. It also comprises questions that test your memory and analytical skills, knowledge of the topics and higher-order thinking skills. Given below is a short overview of the questions asked in this chapter.

There are 28 VSAQs in this chapter that is based on the determination of the order of the given reaction equations, factors affecting the rate of a chemical reaction, the concept of half-life, reaction parameters. Further, the chapter contains 48 SAQs which ask you to determine the order and rate of the given reaction equation, numerical questions based on rate constant and its unit determination, and calculate the reaction rate and constant for the pseudo-first-order reaction. There are 11 LAQs which are word problems and numerical questions both, based on the concept of the half-life of a reaction, reaction parameters, pre-exponential factor, remaining quantity of reactant and energy of activation.

Our Xam Idea Class 12 Chemistry Solutions Chapter 4 – Chemical Kinetics gives you exposure to multiple concepts based questions such as MCQs, skill-developing questions, and application-based questions.

All these questions are answered comprehensively in Xam Idea Class 12 Chemistry Solutions Chapter 4 – Chemical Kinetics. These are precise solutions that help you learn effectively. They give you an ample amount of practice on different concepts learnt and help you master the concepts of the chapter quickly and effectively. Part B of Xam Idea Class 12 Chemistry Solutions Chapter 4  comprises all-encompassing and detailed solutions to several model papers and previous year’s question papers. You are advised to regularly practice them so that you get comfortable with the exam environment and exam pattern.

### Benefits of Xam Idea Class 12 Chemistry Chapter 4 – Chemical Kinetics

Xam Idea Class 12 Chemistry Solutions Chapter 4 – Chemical Kinetics is very helpful for you. Some of the distinct advantages are as follows.

• They are easy to understand and keep you conceptually clear, helping you score good marks in your board examinations as well as excel in competitive exams.
• They are concise and accurate solutions.
• They are interactive and make the learning process efficient.
• They provide with important tips and techniques to solve the questions related to chemical kinetics.
• This chapter is a source of numerical questions which fetch complete marks when solved correctly, so out solutions describe the correct way to solve numerical questions in a step by step methodology.
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