Understanding Rate Laws and Reaction Kinetics in Chemistry
This chapter explores the concept of rate laws and how they relate to the rates of chemical reactions. The rate of a reaction is influenced by the concentration of reactants, described by the rate law expression. For a general reaction A + B, the rate is proportional to the concentration of A and B, given by Rate = k[A]^a[B]^b. Through experimental data involving H2 and Cl2 reactions, we can determine the rate expression and the rate constant k. This understanding is crucial for predicting reaction behaviors in various chemical processes.
Understanding Rate Laws and Reaction Kinetics in Chemistry
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Presentation Transcript
Chapter 18 Notes, part IV Rate Law Problems
Rate Laws • Earlier we discussed that the rate at which a reaction goes is dependent on the concentration of the reactants.
Rate Laws • If the reaction is AaB, then the rate of reaction is dependent on the concentration of A. • So: • Rate=k[A]a
Or, for A + B a C the rate is • Rate=k[A]a[B]b
Rate Laws • Ideally, the superscript “a” and “b” would correspond to the coefficient of A and B, but because of the complex steps that many reactions undergo forming intermediates, this is not usually the case.
Rate Laws • Because of this, the only way to find out the order (exponent) due to each reactant, you have to experiment!
For the reaction H2 + Cl2a2HCl, the following data was collected: [H2] [Cl2] Initial rate 0.30M 0.30M 1.5x102 0.60M 0.30M 3.0x102 0.30M 0.60M 6.0x102 What is the rate expression? What is k?
