339283-NYB-Kinetics-Fall-2007-

339283-NYB-Kinetics-Fall-2007- - 202-NYB - KINETICSFigure...

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Unformatted text preview: 202-NYB - KINETICSFigure 16.2The wide range of reaction rates.Figure 16.1Reaction rate: the central focus of chemical kineticsFactors That Influence Reaction RateUnder a specific set of conditions, every reaction has its owncharacteristic rate, which depends upon the chemical nature ofthe reactants.Four factors can be controlled during the reaction:1.Concentration - molecules must collide to react;2.Physical state - molecules must mix to collide;3.Temperature - molecules must collide with enough energy to react;4.The use of a catalyst.Figure 16.3The effect of surface area on reaction rate.Figure 16.4Collision energy and reaction rate.Expressing the Reaction Ratereaction rate - changes in the concentrations of reactants orproducts per unit timereactant concentrations decrease while product concentrationsincreaseforA Brate of reaction = -change in concentration of Achange in time= -conc A2-conc A1t2-t1(conc A)-tTable 16.1 Concentration of O3at Various Time in its Reaction with C2H4at 303KC2H4(g) + O3(g) C2H4O(g) + O2(g)Time (s)Concentration of O3(mol/L)0.00.03.20x10-5(conc A)20.030.040.050.060.010.02.42x10-51.95x10-51.63x10-51.40x10-51.23x10-51.10x10-5-tFigure 16.5The concentrations of O3vs. time during its reaction with C2H4C2H4(g) + O3(g) C2H4O(g) + O2(g)-[C2H4]trate = =-[O3]tFigure 16.6Plots of [C2H4] and [O2] vs. time.Tools of the LaboratoryIn general, for the reactionaA + bB cC + dDrate = 1-= -[A]1[B]1[C]= +1[D]= +atbtctdtThe numerical value of the rate depends upon the substance thatserves as the reference. The rest is relative to the balanced chemical equation.Sample Problem 16.1Expressing Rate in Terms of Changes in Concentration with TimePROBLEM:Because it has a nonpolluting product (water vapor), hydrogen gas is used for fuel aboard the space shuttle and may be used by Earth-bound engines in the near future.2H2(g) + O2(g) 2H2O(g)(a)Express the rate in terms of changes in [H2], [O2], and [H2O] with time.(b)When [O2] is decreasing at 0.23 mol/L*s, at what rate is [H2O] creasing?PLAN:SOLUTION:increasing?Choose [O2] as a point of reference since its coefficient is 1. For every molecule of O2which disappears, 2 molecules of H2disappear and 2 molecules of H2O appear, so [O2] is disappearing at half the rate of change of H2and H2O.-12[H2]t= -[O2]t= +[H2O]t120.23mol/L*s= +[H2O]t12; = 0.46mol/L*s[H2O]trate =(a)[O2]t-= -(b)Sample Problem 16.2 Determining Reaction Order from Rate LawsPROBLEM:For each of the following reactions, determine the reaction order with respect to each reactant and the overall order from the given rate law....
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This note was uploaded on 12/04/2009 for the course CHEM 120 taught by Professor Johnmichael during the Spring '09 term at Tennessee Martin.

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339283-NYB-Kinetics-Fall-2007- - 202-NYB - KINETICSFigure...

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