CHEM 1120 1st Edition Lecture 5 Outline of Current Lecture 1. Chemical kinetics2. Factors that affect reaction rates3. Types of rates measured4. Average rates and plotting data, gathering information from plotted data5. Concentration and Rate LawsCurrent LectureChapter 14-Chemical Kinetics- Chemical Kineticso when we study the rate (or speed) at which a chemical process occurs.o Also, has to deal with reaction mechanism-a molecular-level view of the path from reactants to productso Examples of Chemical Kinetics: speed of reaction at which an apple goes bad, speed at which oxidation occurs on steel.14.1- Factors that affect reaction rateso Physical state-  The more readily the reactants collide, the more rapidly they react Homogeneous reactions are often faster Heterogeneous reactions that involve solids are faster if the surface area is increased. (ex/ a fine powder reacts faster than a pellet or tablet)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. example: fine powder vs solid block vs gas vs liquido Reactant concentration-  Increasing reactant concentration generally increases reaction rate Since there are more molecules, more collisions occur example: dilute vs concentratedo Reaction Temperature-  Reaction rates generally increase with increasing temperature Kinetic energy of molecules is related to temperature. At higher temperatures, molecules move more quickly example- boiling eggso Catalysts-  Affect rate without being in the overall balanced equation Affect kinds of collisions, changing the mechanism (individual reactions that are part of the pathway from reactants to products Critical in many biological reactions  example: alcohol sensitivity related to aldehyde dehydrogenase, or car catalytic converters 14.2- Rate is a change in concentration over a time period.- Types of rates measuredo Average rate Final minus initial concentration/time Rate of reaction averaged over a period of time Slide 22o Instantaneous rate Slope of the tangent lineo Initial rate The instantaneous rate at time zero Often the rate of interests for chemists- Average rate of appearance- Average rate of disappearance - Plotting rate datao Gives us more information about rateo Instantaneous rate Slope of curve at one point in time- Relative rateso Rate is dependent on stoichiometry- Average rate for loss of reactants-- Average rate for formation of productso Average rate= -change in c/change in to- Reaction rateo The change in concentration per unit time taking into account stoichiometry and reaction directions.14.3 Concentration and Rate Laws Rate= k[A]^m[B]^no K= rate constant depends on tempo Expoonets define the order of the reaction m is the order of the reaction with respect to A n is order of reaction with respect to B (m+n) is the overall reaction order m and n are both usually integerso Often found that m and n do not need to equal a and b AND must be determinedo Reaction