# Rates of Reaction

Chemistry AS :)

Definitions and how to explain:

• The Collision Theory
• Increasing Concentration/ Pressure on the rate of reaction
• Increasing Temperature on the rate of reaction
• Addition of a Catalyst on the rate of reaction
• Activation Enthalpy
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• Created by: VicC
• Created on: 25-05-09 20:49

## Rates of Reaction

affected by:

• concentration
• pressure
• a catalyst
• surface area
• particle size
• temperature
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## THE COLLISION THEORY

For a reaction to occur, reactant particles must collide AND their combined kinetic energy must be equal to or greater than the activation energy for the reaction.

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## Affecting the Rate of Reaction...

increasing CONCENTRATION/ PRESSURE:

• means more particles per cm3
• hence, more collisions per second
• hence, rate of reaction INCREASES

! no mention of activation energy !

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## Affecting the Rate of Reaction...

increasing TEMPERATURE:

• particles have more kinetic energy
• so collisions have more knietic energy
• collisions occur more frequently
• as a greater proportion of collisions will equal or exceed the minimum activation energy needede to react
• hence, the rate of reaction INCREASES
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## Affecting the Rate of Reaction...

• provides an alternative pathway for the making and breaking of bonds
• hence, providing a lower activation energy
• so a greater proportion of collisions will equal or be greater than the minimum activation energy needed for the reaction to occur
• hence, the rate of reaction INCREASES
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## ACTIVATION ENTHALPY/ ENERGY

• The minimum combined kinetic energy required by a pair of colliding particles before a reaction will occur.

or

• The energy required to allow bonds in the reactants to stretch and break as the new bonds form in the products.
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