AS Chemistry OCR A - Rates of Reaction - Revision Cards in A Level and IB Chemistry

Collision Theory

Increase in concentration
- Increase in amount of molecules per unit volume
- Increases the frequency of collisions
Increase in pressure of a gas
- Increase in amount of molecules per unit volume.
- increases the frequency of collisions
Increase the temperature
- Increases the energy of the molecules.
  - Increases the speed of the molecules
    - Increases the frequency of collisions
  - Increases the chance that colliding molecules have higher energy than the activation energy
    - Increases the rate of successful collisions
Use of catalyst
- Provides secondary route to the products with a lower activation energy.
- Highten the chance that colliding molecules will have higher energy than the new activation energy.
- Increases the rate of successful collisions.

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Increase surface area of a solid.
- Increase the amount of interfacing molecules.
  - Increase the frequency of collisions

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(http://www.4college.co.uk/as/atm/rate.gif)

The area under the graph is the amount of molecules in the chemical system.
- Stays the same
The shaded area shows the amount of molecules with activation energy.
The curve should start from the origin, as there are no molecules with no energy.
Catalysts provide a secondary route of reaction with lower activation energy.
- Add a secondary marker to the left of activation energy labelled catalyst.

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(http://puu.sh/nF9E5/a5bc1883b6.png)

Because the area under the graph remains constant:
- As the temperature increases the height of the peak lowers and moves to the right.
- As the temperature decreases the peak heightens and moves to the left.

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