Kinetics: the theory1. making more collisions have favorable orientation;2. locally increasing concentrations on its surfaces;3. providing a series of simple steps rather than one highenergy one;4. providing a better attacking group which is regeneratedlater;5. increasing the reactivity of the reactive site.ENo.ofparticlesEEREM-energy11
11 Kinetics: the theory 1. making more collisions have favorable orientation; 2. locally increasing concentrations on its surfaces; 3. providing a series of simple steps rather than one high energy one; 4. providing a better attacking group which is regenerated later; 5. increasing the reactivity of the reactive site
Kinetics: the theoryRelating the theory to the rate equationRate = k[A]x[B]k = Ae-E/RTconcentration changeschange ratek is temperature dependentand k depends on the activation energyand so is affected by adding a catalyst12
12 Kinetics: the theory Relating the theory to the rate equation Rate = k[A]x [B]y k = Ae-E A /RT concentration changes change rate k is temperature dependent and k depends on the activation energy and so is affected by adding a catalyst
Kinetics: the theoryRate determining stepsLike roadworks on a motorway, the slowest step in a multistepreaction controls the overall rate.e.g.0H+ slowlyfast reaction11CH,CCH3CHI3active enol formwith I2so rate depends on [propanone] not [iodine]reaction is 1st order w.r.t. propanone, zero w.r.t. iodine13
13 Kinetics: the theory Rate determining steps Like roadworks on a motorway, the slowest step in a multistep reaction controls the overall rate. e.g. CH3CCH3 active enol form CHI3 so rate depends on [propanone] not [iodine] reaction is 1st order w.r.t. propanone, zero w.r.t. iodine O H+ slowly fast reaction with I2
Kinetics: the theoryWordsWords and Expressionscollision: collideactivation energy; pre-exponential factorpopulationpropanone = acetoneenol14
14 Kinetics: the theory Words collision: collide activation energy; pre-exponential factor population propanone = acetone enol Words and Expressions
CatalysisCatalysis: changing the rate of reactions by adding asubstance which does not get used upHETEROGENEOUS CATALYSISe.g. H2 + I, 2HIunsuccessful collision:orientationwrongUncatalyzedfavourableorientation8EA=157kJmol-11526kJmof-1
15 Catalysis Catalysis: changing the rate of reactions by adding a substance which does not get used up HETEROGENEOUS CATALYSIS e.g. H2 + I2 2HI Uncatalyzed