Reaction Rates

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Reaction Rates

• An Introduction to Chemical Kinetics

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Chemical Kinetics deal with

• reaction rates and reaction mechanisms

Steps of Reaction
Speed of Reaction
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Particle Energy

• Molecules must have sufficient energy for a
  reaction to occur.
• The energy involved in a reaction is represented
  on a reaction coordinate.

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What can be found on a reaction coordinate?

• Activation energy
• the energy required to start a reaction
• If the reaction is exothermic
• More energy is released than entering the
  reaction
• If the reaction is endothermic
• More energy is entering the reaction than is
  released

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Collision Theory

• When do molecules react?

• When they collide!!!

Collision Reaction
(More collisions
Faster Reaction)
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What factors can affect the rate of reaction?
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CATALYSTS

• By adding a catalyst, the reaction rate
  increases.
• Why?

• Catalysts lower the activation energy.
• (less energy needed to start the reaction!)

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TEMPERATURE

• As temperature increases, the reaction rate
  increases.
• Why?

Higher temperature More K.E. (movement)
More Collisions
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CONCENTRATION

• As the concentration of the reactants increases
  (more molecules/volume), the rate increases.
• Why?

Less room between reactants More collisions
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SURFACE AREA

• (For liquids solids) As the surface area of
  reactants increases the rate increases.
• Why?

• Contact between the reactants is greater.

• How can we increase the surface area?

• stir or mix a Liquid
• crush or break a solid

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PRESSURE

• If at least one reactant is a GAS, as the
  pressure increases, the rate increases.
• Why?

Reactants are squeezed closer together more
collisions

• How can you raise pressure?

Decrease the volume or Increase the amount of gas
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NATURE OF THE REACTANTS

• As the number of bonds to be broken increases,
  the reaction rate decreases.
• Bond breaking requires energy!!!!!