AQA AS Chem Unit 2- Collision Theory

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Kinetics is the study of factors which affect rates of chemical reactions i.e. how quickly they take place. There is a large variation in reaction rates. 'Popping' a test tube full of Hydrogen is over in a fraction of a second however, the complete rusting away of a nail could take several years. Reactions can be speeded up or slowed down by changing the conditions.

For a reactions to take place between two particles, they must collide, and do so with enough energy to break bonds. The collision must also take place between the parts of the molecule that are going to react together, so orientation is also important. In order to get a lot of collisions, there needs to be a large amount of molecules in a small volume. For the particles to have enough energy to break bonds they need to be moving fast. So, for a fast reaction rate there must be plenty of rapidly moving particles in a small volume.

Most collisions between molecules do not lead to reaction. They either do not have enough energy, or are in the wrong orientation.

Factors affecting the rate of chemical reactions

1) Increasing the temperature: This increases the speed of the molecules, which in turn increases both their energy and the number of collisions.

2) Increasing the concentration of a solution: If there are more particles present in a given volume, collisions are more likely; therefore the reaction rate would be faster. However, as a…


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