Core Teaching Resources Chemistry Answers Chapter 15

Core Teaching Resources Chemistry Answers Chapter 15 Core Teaching Resources Chemistry Answers Chapter 15 Chemical Kinetics This document provides answers to the exercises and problems found in Chapter 15 of the Core Teaching Resources Chemistry textbook The chapter focuses on chemical kinetics the study of reaction rates and mechanisms It covers the following key concepts I to Chemical Kinetics 11 Rates of Chemical Reactions Introduces the concept of reaction rate defines average and instantaneous rates and explores the factors influencing reaction rate 12 Rate Laws and Integrated Rate Laws Introduces the concept of rate laws different orders of reactions integrated rate laws for zero first and second order reactions and their graphical representations 13 Activation Energy and the Arrhenius Equation Defines activation energy and explains its relationship to reaction rate introduces the Arrhenius equation and describes its use in determining activation energy and preexponential factor II Reaction Mechanisms 21 Elementary Steps and the RateDetermining Step Defines elementary steps molecularity and the ratedetermining step in multistep reactions 22 Mechanisms and Rate Laws Explains how to derive rate laws from proposed mechanisms and how to use experimental data to determine the ratedetermining step 23 Catalysis Defines catalysts and their impact on reaction rates explains the difference between homogeneous and heterogeneous catalysis and provides examples of catalytic reactions III Applications of Chemical Kinetics 31 Environmental Chemistry Illustrates the use of chemical kinetics in understanding atmospheric reactions pollution control and environmental remediation 32 Biochemistry Discusses the importance of chemical kinetics in enzyme catalysis metabolic pathways and drug design 2 33 Industrial Chemistry Examines the use of chemical kinetics in optimizing industrial processes controlling reaction conditions and designing new catalysts Answers to Chapter 15 Exercises and Problems 1 Rates of Chemical Reactions Exercise 11 The average rate of a reaction is the change in concentration of a reactant or product over a specific time interval The instantaneous rate is the rate of the reaction at a specific point in time Exercise 12 Factors affecting reaction rate include Concentration of reactants Increasing the concentration of reactants increases the rate of the reaction Temperature Increasing the temperature generally increases the rate of the reaction Surface area Increasing the surface area of a solid reactant increases the rate of the reaction Presence of a catalyst A catalyst speeds up the rate of a reaction without being consumed in the process Problem 11 a Calculate the average rate of disappearance of NO2 over the first 20 seconds b Calculate the instantaneous rate of disappearance of NO2 at 10 seconds c Calculate the average rate of appearance of O2 over the first 20 seconds Problem 12 Consider the reaction 2A B 3C a Express the rate of the reaction in terms of the rate of disappearance of A b Express the rate of the reaction in terms of the rate of appearance of C 2 Rate Laws and Integrated Rate Laws Exercise 21 The rate law expresses the relationship between the rate of a reaction and the concentrations of reactants The order of a reaction with respect to a particular reactant is the exponent in the rate law for that reactant Exercise 22 The integrated rate law relates the concentration of a reactant to time Zero order reaction At kt A0 First order reaction lnAt kt lnA0 Second order reaction 1At kt 1A0 Problem 21 The decomposition of N2O5 is a firstorder reaction a Calculate the rate constant for the reaction b Calculate the halflife of the reaction Problem 22 The reaction between H2 and I2 is second order Determine the rate constant 3 for the reaction 3 Activation Energy and the Arrhenius Equation Exercise 31 Activation energy is the minimum energy required for molecules to react The Arrhenius equation relates the rate constant of a reaction to its activation energy and temperature Exercise 32 The preexponential factor is a constant that reflects the frequency of collisions between reactants Problem 31 The activation energy for a certain reaction is 50 kJmol Calculate the rate constant at 25C if the rate constant at 50C is 10 x 103 s1 Problem 32 The rate constant for a reaction is 25 x 104 s1 at 300 K What is the rate constant at 350 K if the activation energy is 60 kJmol 4 Reaction Mechanisms Exercise 41 An elementary step is a single step in a reaction mechanism Molecularity is the number of molecules involved in an elementary step The ratedetermining step is the slowest step in a reaction mechanism Exercise 42 The rate law for a multistep reaction is determined by the ratedetermining step Problem 41 Propose a mechanism for the reaction 2NO O2 2NO2 Problem 42 Determine the rate law for the reaction 2NO O2 2NO2 based on the following proposed mechanism Step 1 2NO N2O2 fast Step 2 N2O2 O2 2NO2 slow 5 Catalysis Exercise 51 A catalyst speeds up the rate of a reaction without being consumed in the process Homogeneous catalysis occurs when the catalyst and reactants are in the same phase Heterogeneous catalysis occurs when the catalyst and reactants are in different phases Exercise 52 Examples of catalytic reactions HaberBosch process Production of ammonia from nitrogen and hydrogen using an iron catalyst Catalytic converter Oxidizes carbon monoxide and hydrocarbons in exhaust gases using a platinumrhodium catalyst Problem 51 Explain how a catalyst can increase the rate of a reaction Problem 52 Describe the role of enzymes in biological catalysis 4 6 Applications of Chemical Kinetics Exercise 61 Chemical kinetics is essential in understanding and controlling environmental processes including atmospheric reactions pollution control and environmental remediation Exercise 62 Chemical kinetics plays a vital role in biochemistry particularly in enzyme catalysis metabolic pathways and drug design Exercise 63 Chemical kinetics is used in industrial chemistry to optimize processes control reaction conditions and design new catalysts Problem 61 Describe how chemical kinetics is used to study atmospheric reactions Problem 62 Discuss the application of chemical kinetics in drug design Problem 63 Explain how chemical kinetics is used to optimize industrial processes Note This document provides a brief overview of the answers and solutions to the exercises and problems in Chapter 15 of Core Teaching Resources Chemistry It is important to refer to the textbook and other resources for a more comprehensive understanding of the concepts discussed