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Series: Chemistry: Collision Model & Arrhenius Equation


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About this Series

  • Lessons: 3
  • Total Time: 0h 26m
  • Use: Watch Online & Download
  • Access Period: Unlimited
  • Created At: 10/22/2009
  • Last Updated At: 04/11/2011

This three part series will discuss and teach us about temperature and rates. According to the collision model, the reaction rate is determined by the collision rate and the fraction of collisions that successfully produce products. One factor determining the fraction of collisions that successfully produce products is the energy required for the reaction to occur. This factor is the activation energy (Ea). The activation energy is the difference in energy between the reactants (A and BC) and an activated complex (A--B--C). Slower moving reactants have lower kinetic energy. They therefore have a smaller probability of having enough energy to form the activated complex. Kinetic energy is temperature dependent. These concepts lead to a mathematical representation of the fraction of collisions with enough energy to react (f). The collision rate depends on the concentrations of reactants and their molecular speeds.

Then we will learn about the Arrhenius equation. The reaction rate increases as temperature
increases. For example, light sticks react more slowly in ice water than at room temperature, and react even faster when placed in hot water. Food is refrigerated to slow down decomposition reactions. The relationship between the reaction rate and temperature is expressed by the Arrhenius equation. The Arrhenius equation relates the rate constant (k) to the frequency factor (A) and the fraction of collisions with enough energy to react (f). This equation can be used to find the activation energy (Ea) from a set of experimental data.

Concluding this series we will learn how to use the Arrhenius equation. The Arrhenius equation can be rewritten for two temperatures, allowing for comparisons between those two temperatures. This is done by subtracting the Arrhenius equation for a temperature T1 from the Arrhenius equation for a temperature T2. This eliminates the frequency factor (A). The Arrhenius equation is useful for predicting the rate constant (k) of a reaction at a given temperature. The activation energy (Ea) can be calculated when the rate constants are known at two different temperatures.

This series of lessons was selected from a broader, comprehensive course, Chemistry. This course and others are available from Thinkwell, Inc. The full course can be found at The full course covers atoms, molecules and ions, stoichiometry, reactions in aqueous solutions, gases, thermochemistry, Modern Atomic Theory, electron configurations, periodicity, chemical bonding, molecular geometry, bonding theory, oxidation-reduction reactions, condensed phases, solution properties, kinetics, acids and bases, organic reactions, thermodynamics, nuclear chemistry, metals, nonmetals, biochemistry, organic chemistry, and more. The course features three renowned chemistry professors: Dean Harman, a professor of Chemistry at the University of Virginia and Gordon Yee, an associate professor of Chemistry at Virginia Tech and Tarek Sammakia, a professor of chemistry at the University of Colorado at Boulder.

About this Author

2174 lessons

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Lessons Included

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