Collision Theory of Reaction Rates
This theory makes the assumption that, for a reaction to occur, there must be collisions between the reacting species. This means that the rate of reaction depends on two factors: the number of collisions per unit time, and the fraction of these collisions that are successful because enough energy is involved.
Go To Collision Theory #1 for a continuation
Go To Collision Theory # for a representative cartoon!
Five important factors control the rate of a chemical reaction.
1. The nature of the reactants. Some elements and compounds, because of the bonds broken or formed, react more rapidly with each other.
2. The surface area exposed. Since most reactions depend on the reactants coming into contact, the surface exposed proportionally affects the rate of
3. The concentrations. The reaction rate is usually proportional to the concentrations of the reactants.
4. The temperature. A temperature increase of 10° C above room temperature usually causes the reaction rate to double or triple.
5. The catalyst. Catalysts can either speed up or slow down the rate of a reaction. A catalyst does not change itself nor the reaction. It only lowers the activation energy. See below:
Activation Energy & Catalysts
Often a reaction rate may be increased or decreased by affecting the activation energy, that is, the energy necessary to cause a reaction to occur. A catalyst is a substance that is introduced into a reaction to either speed up or slow down the reaction. This is accomplished by changing the amount of activation energy needed.
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Go To Effects of Catalysts for a Diagram of the Effects of Catalysts on the Activation Energy
Enzymes are catalysts in the body.
Go To Enzymes for a energy diagram comparisons
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