The Boltzmann Distribution

Front 1

The Boltzmann distribution

Back 1

The distribution of energies of molecules at a particular temperature, often shown as a graph.

Front 2

Important features of the boltzmann distribution

Back 2

> Area under the curve is equal to the total number of molecules in the sample
> No molecules in the system with zero energy - curve starts at origin
> No maximum energy for a molecule - curve gets closer but doesn't touch the x- axis
> ONLY molecules with an energy greater than the activation energy are able to react

Front 3

Effect of temperature

Back 3

> Kinetic energy in molecules increases - The boltzmann distribution flattens and shifts to the right
> As temperature increases the rate of reaction also increases

Front 4

Why does the rate of reaction increase?

Back 4

> More collisions take place in a certain time
> Molecules move faster and have more kinetic energy
> Higher proportion of molecules have an energy which is greater than the activation energy
> More collisions lead to a chemical reaction

Front 5

Effect of a catalyst on reaction rate

Back 5

> Activation energy is reduced
> On collisions more molecules in the system will overcome the new lower activation energy of the reaction
> More successful collisions over a length of time
> Reaction rate will increase