1. Chemical Kinetics Nancy Griffeth January 8, 2014 Funding for this workshop was provided by the program “Computational Modeling and Analysis of Complex Systems,” an NSF Expedition in Computing (Award Number 0926200).

2. Chemical Reactions A and B are reactants, whose concentration decreases until the completion of the reaction. C is a product, whose concentration increases until the completion of the reaction. The rate at which the concentration of reactants decreases and the concentration of the product increases is is reaction rate. A + B C

3. Effect of Concentration, Temperature, and Catalysts The greater the concentration of reactants the likelihood that molecules will collide increases. At high temperatures, reactant molecules have more kinetic energy and have a greater chance of colliding. Catalysts speed up reactions by changing the mechanism by which they occur. A + B C

4. Chemical Reactions How can we represent the concentrations of molecules in a solution? – How can we keep track of the changes in concentrations? A + B C

5. Reaction Rate We represent the concentration change over time as differential equations. Rate = - 1 Δ [A] = - 1 Δ[B] = 1 Δ [C] a Δt b Δt c Δt Reactants decrease Products increase (negative)(positive) aA + bB cC

6. Rate Laws Rate laws show the relationship between the reaction rate and the concentrations of reactants. – k is a constant that has a specific value for each reaction. It’s value is determined experimentally. rate = k [reactants] rate = k [A] α [B] β A + B C

7. Rate Laws rate = k [A] [B] The overall order of a reaction is determined by the sum of the exponents. – In this case the reaction is second order. Write a rate for the above reaction and state its overall order. A + B C A + B + C D

8. Integrating Rate Laws First order rate laws can be written as : rate = - d [A] = k [A] d t Integration of this rate law produces the integrated rate law. d [A] =- k d t [A] At t = 0, [A] = [A] 0 [A] = [A] 0 e - k t A B