CHEM 111 Kinetics Review Tom Teets

CHEM 111 Kinetics Review Tom Teets - Kinetics Review...


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Kinetics Review Prepared by Tom Teets 11/01/05 I. General Kinetics Stuff - Factors that affect the rate: 1. Nature of reactants (rate for gases>liquids>solids, electron transfer reactions and reactions in solution also very fast) 2. Concentration (or Pressure) of Reacting Species- Greater concentrations almost always yield greater rates: increases the number of productive collisions between molecules. 3. Temperature- Increasing temperature increases the reaction rate by shifting the Boltzman distribution (remember this?) Arrhenius equation relates temperature (T) to rate constant (k): ln(k 2 /k 1 )=(-E a /R)(1/T 2 -1/T 1 ) 4. Presence of a catalyst- catalysts increase rate -Rate equation: General Form: Rate = k[A] x [B] y …, where A, B, … are the reactants. Can also be written in terms of Pressure for gases. -Units of rate constant: M -(n-1) t -1 , where n is the overall rate order (sum of exponents in rate equation) and t is any unit of time. For gases: atm -(n-1) t -1 II. Initial Rate Method - Using a table relating different reactant concentrations to different initial rates, you can solve for the rate orders and the rate constant. - General method for solving these types of problems: 1. For each run or trial in the data table, write rate equations using the general form rate = k [A] x [B] y . 2. Choose two runs that only differ in the concentration of 1 reactant, and divide their rate equations: 22 11 [] 2 1[ ] [ ] x y x y kA B rate rate k A B = k always divides out, and the concentration that stays the same between run 1 and run 2 also divides out, leaving you with only one variable (an exponent) to solve for.
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CHEM 111 Kinetics Review Tom Teets - Kinetics Review...


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