14-4 Zero-Order Reactions

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Slide 1 of 61 14-4 Zero-Order Reactions A → products R rxn = k [A] 0 R rxn = k [k] = mol L -1 s -1
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14-4 Zero-Order Reactions. A → products. R rxn = k [A] 0. R rxn = k. [ k ] = mol L -1 s -1. -d[A]. Move to the infinitesimal. = k. d t. t. [A] t. - . . d[A]. = k. d t. [A] 0. 0. Integrated Rate Law. - Δ [A]. = k. Δ t. And integrate from 0 to time t. - PowerPoint PPT Presentation

Transcript of 14-4 Zero-Order Reactions

  • 14-4 Zero-Order ReactionsA productsRrxn = k [A]0Rrxn = k[k] = mol L-1 s-1

  • Integrated Rate Law-[A]t + [A]0 = kt[A]t = [A]0 - ktt-[A]= kAnd integrate from 0 to time t

  • 14-5 First-Order ReactionsH2O2(aq) H2O(l) + O2(g)= -k[H2O2] d[H2O2 ]dt[k] = s-1

  • First-Order Reactions

  • Half-Lifet is the time taken for one-half of a reactant to be consumed.- ln 2 = -kt

  • Half-LifeButOOBut(g) 2 CH3CO(g) + C2H4(g)

  • Some Typical First-Order Processes

  • 14-6 Second-Order ReactionsRate law where sum of exponents m + n + = 2.

    A products

  • Second-Order Reaction

  • Testing for a Rate LawPlot [A] vs t.Plot ln[A] vs t.Plot 1/[A] vs t.

  • 14-7 Reaction Kinetics: A SummaryCalculate the rate of a reaction from a known rate law using:

    Determine the instantaneous rate of the reaction by:

    Rate of reaction = k [A]m[B]n .Finding the slope of the tangent line of [A] vs t or,Evaluate [A]/t, with a short t interval.

  • Summary of KineticsDetermine the order of reaction by:Using the method of initial rates.Find the graph that yields a straight line.Test for the half-life to find first order reactions.Substitute data into integrated rate laws to find the rate law that gives a consistent value of k.

  • Summary of KineticsFind the rate constant k by:

    Find reactant concentrations or times for certain conditions using the integrated rate law after determining k.Determining the slope of a straight line graph.Evaluating k with the integrated rate law.Measuring the half life of first-order reactions.

  • Worked Examples Follow:

  • CRS Questions Follow:

  • In the diagram to the right is a plot of the concentrations of all reactants and products as a function of time for a particular reaction.Which of the following statements is correct?5. Cannot tell with the information given.1. The reaction is second order.2. The blue curve represents the time dependence on a particular product.3. The rate constant for the reaction could have units of s-1.4. The product represented by the green line is produced almost twice as fast as the product represented by the red line.

  • In the diagram to the right is a plot of the concentrations of all reactants and products as a function of time for a particular reaction.Which of the following statements is correct?5. Cannot tell with the information given.1. The reaction is second order.2. The blue curve represents the time dependence on a particular product.3. The rate constant for the reaction could have units of s-1.4. The product represented by the green line is produced almost twice as fast as the product represented by the red line.

  • Reaction A has a rate constant which is equal to 16.2 L mol-1 s-1. A plot relating the concentrations of the reactants and products with time is plotted for reaction B to the right.In this question, two reactions are considered.Reaction A is first order and Reaction B is second order.2. Reaction A is second order and Reaction B is first order.3. Both reactions are first order.4. Both reactions are second order.

  • Reaction A has a rate constant which is equal to 16.2 L mol-1 s-1. A plot relating the concentrations of the reactants and products with time is plotted for reaction B to the right.In this question, two reactions are considered.Reaction A is first order and Reaction B is second order.2. Reaction A is second order and Reaction B is first order.3. Both reactions are first order.4. Both reactions are second order.

  • Some data for the decomposition of dinitrogen pentoxide are plotted to the right. Which of the following statements is correct?1. The rate constant is 81.7 s.3. The units of the rate constant are s.4. The reaction is first order in N2O5.5. The reaction is third order in N2O5.2. The rate constant is

  • Some data for the decomposition of dinitrogen pentoxide are plotted to the right. Which of the following statements is correct?1. The rate constant is 81.7 s.3. The units of the rate constant are s.4. The reaction is first order in N2O5.5. The reaction is third order in N2O5.2. The rate constant is

    Chemistry 140 Fall 2002Chemistry 140 Fall 2002Chemistry 140 Fall 2002Chemistry 140 Fall 2002Chemistry 140 Fall 2002Figure: 14-T05

    Title: Reaction kinetics: A summary for the hypothetical reaction A --> Products

    Caption: A summary of zeroth, first, and second order rate laws.Chemistry 140 Fall 2002Chemistry 140 Fall 2002Chemistry 140 Fall 2002Chemistry 140 Fall 2002