AQA AS Chemistry Unit 2: Kinetics


Chemistry Unit 2: Kinetics

The Collision Theory

  • For a reaction to occur the particles must collide with enough energy to break bonds

  • To get a lot of collisions you need many particles in a small volume

  • Particles also need to be moving fast to breaks bonds

    Most Collisions between molecules do not lead to reaction. They either do not have enough energy or are of the wrong orientation

Factors that Increase Rate of Reaction:

Temperature: Increase then increases the speed of molecules which increases their energy and number of collisions

Concentration of Solution: Increase means there are more particles in a given volume making collisions more likely. As the reactants are used up concentration falls reducing rate of reaction

Pressure: Increase in gas reaction has the same effect as concentration

Surface Area: Larger means more particles are available to collide with molecules meaning breaking a solid into smaller pieces increases rate of reaction as more sites for reaction

Catalyst: Changes the rate of a chemical reaction without being chemically changed itself

For a collision to occur the molecule must have a certain minimum energy to start breaking the bonds

The Maxwell-Boltzmann Distribution

  • The energy of a particle depends on its speed so particles ave a range of


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