Chemistry 132 NTRates of ReactionChem 132 NTPowerPoint PresentationTipsReasons for Studying KineticsSlide 7Reaction RatesSlide 9Slide 10Slide 11Slide 12Slide 13Slide 14Factors Affecting Reaction RatesSlide 16Slide 17Figure 13.2 Catalytic decomposition of hydrogen peroxideSlide 19Slide 20Figure 13.3 Effect of large surface area on the rate of reaction.SummaryDefinition of Reaction RateDefinition of Reaction RatesSlide 25Figure 13.4 The instantaneous rate of reactionSlide 27Figure 13.5 Calculation of the average rate.Slide 29Slide 30A Problem to ConsiderSlide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Experimental Determination of Reaction RatesSlide 43Figure 13.6 An experiment to follow the concentration of N2O5 as the decomposition proceedsSlide 45Dependence of Rate on ConcentrationSlide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Slide 54Slide 55Slide 56Slide 57Slide 58Slide 59Slide 60A Problem To ConsiderSlide 62Slide 63Slide 64Slide 65Slide 66Slide 67HomeworkOperational SkillsSlide 7011111Chemistry 132 NTWe are what we repeatedly do. Excellence is , then, not an act, but a habitAristotleRates of ReactionChapter 13Module 1Sections 13.1, 13.2, and 13.3The burning of steel wool33333Chem 132 NTChemistry 132 NT (First Exam) Chapter 13: Reaction Rates Chapter 14: Chemical Equilibrium Chapter 15: Acids and Bases Each chapter broken into modules (3 or 4) Tutorial quiz at end of each module Homework assignment for each module4444455555TipsKeep your text book handy.After this presentation, read sections 13.1-13.3.Take the tutorial quiz.Pace yourself.66666Reasons for Studying KineticsThe production of chemicals.77777Reasons for Studying KineticsThe production of chemicals.88888Reaction RatesChemical reactions require varying lengths of time for completion.This “reaction rate” depends on the characteristics of the reactants and products and the conditions under which the reaction is run. (see Fig. 13.1)By understanding how the rate of a reaction is affected by changing conditions, one can learn the details of what is happening at the molecular level.99999Reaction RatesThe questions posed in this chapter will be:What conditions will affect the rate of a reaction?How is the rate of a reaction measured?How do you express the relationship of rate to the variables affecting the rate?What happens on a molecular level during a chemical reaction?1010101010Reaction RatesChemical kinetics is the study of reaction rates, how reaction rates change under varying conditions, and what molecular events occur during the overall reaction.Concentration of reactants.What variables affect reaction rate?1111111111Reaction RatesChemical kinetics is the study of reaction rates, how reaction rates change under varying conditions, and what molecular events occur during the overall reaction.Concentration of a catalyst.What variables affect reaction rate?1212121212Reaction RatesChemical kinetics is the study of reaction rates, how reaction rates change under varying conditions, and what molecular events occur during the overall reaction.Temperature at which the reaction occurs.What variables affect reaction rate?1313131313Reaction RatesChemical kinetics is the study of reaction rates, how reaction rates change under varying conditions, and what molecular events occur during the overall reaction.Surface area of a solid reactant or catalyst.What variables affect reaction rate?1414141414Reaction RatesChemical kinetics is the study of reaction rates, how reaction rates change under varying conditions, and what molecular events occur during the overall reaction.Let’s look at each in more detail.What variables affect reaction rate?1515151515Factors Affecting Reaction RatesConcentration of reactantsMore often than not, the rate of a reaction increases when the concentration of a reactant is increased.Increasing the population of reactants increases the likelihood of a successful collision.In some reactions, however, the rate is unaffected by the concentration of a particular reactant, as long as it is present at some concentration.1616161616Concentration of a catalyst.A catalyst is a substance that increases the rate of a reaction without being consumed in the overall reaction.The catalyst, generally, does not appear in the overall balanced chemical equation (although its presence may be indicated by writing its formula over the arrow).Factors Affecting Reaction Rates)g(2)l(2 )aq(HBr)aq(22OOH2OH2  1717171717Concentration of a catalyst.Factors Affecting Reaction Rates)g(2)l(2 )aq(HBr)aq(22OOH2OH2  Figure 13.2 shows the HBr catalyzed decomposition of H2O2 to H2O and O2.A catalyst speeds up reactions by reducing the “activation energy” needed for successful reaction.A catalyst may also provide an alternative mechanism, or pathway, that results in a faster rate.Figure 13.2 Catalytic decomposition of hydrogen peroxideThe hydrogen peroxide decomposes rapidly when hydrobromic acid is added to produce oxygen gas bubbles and the red color of Br2.1919191919Factors Affecting Reaction RatesTemperature at which a reaction occurs.Usually reactions speed up when the temperature increases.A good “rule of thumb” is that reactions approximately double in rate with a 10 oC rise in temperature.2020202020Factors Affecting Reaction RatesSurface area of a solid reactant or catalyst.Because the reaction occurs at the surface of the solid, the rate increases with increasing surface area.Figure 13.3 shows the effect of surface area on reaction rate.Figure 13.3 Effect of large surface area on the rate of reaction.Very finely divided cellulose ignites easily to produce a yellow flame. The powder has a large surface area per volume and burns rapidly in air.2222222222SummaryConcentration of reactantsConcentration of catalystsTemperature of reactionSurface area of solid reactants and catalysts2323232323Definition of Reaction RateThe reaction rate is the increase in molar concentration of a product of a reaction per unit time. It can also be expressed as the decrease in molar concentration of a reactant per unit time.2424242424Definition of Reaction RatesConsider the gas phase decomposition of dintrogen pentoxide.)g(O)g(NO4)g(ON22252If we denote molar concentrations using brackets, then the change in the molarity of O2 would be represented as where the symbol, , (capital Greek delta) means the “change in”.]O[22525252525Then, in a given time