The Collision Theory of Reaction Rates

Flashcards about the collision theory of reaction rates.

Species

Any sort of particle you like - molecule, ion, or free radical.

Reactions involving collisions between two species

Species can only react together if they come into contact with each other; they first have to collide, and then they may react.

Why "may react"?

It isn't enough for the two species to collide - they have to collide the right way around, and they have to collide with enough energy for bonds to break.

Orientation of collision (ethene and hydrogen chloride example)

The reaction can only happen if the hydrogen end of the H-Cl bond approaches the carbon-carbon double bond. Any other collision between the two molecules doesn't work; the two simply bounce off each other.

Energy of the collision

Even if the species are orientated properly, you still won't get a reaction unless the particles collide with a certain minimum energy.

Activation energy

The minimum energy required before a reaction can occur.

Activation energy as a barrier

A barrier to the reaction; only those collisions which have energies equal to or greater than the activation energy result in a reaction.

The Maxwell-Boltzmann Distribution

In any system, the particles present will have a very wide range of energies; For gases, this can be shown on a graph called the Maxwell-Boltzmann Distribution which is a plot of the number of particles having each particular energy.

Area under the Maxwell-Boltzmann curve

A measure of the total number of particles present.

Reaction requirement related to activation energy

Particles must collide with energies equal to or greater than the activation energy for the reaction.