l2 Rate of Reaction

This page is designed to give you a brief overview of the terms used in this unit and the fundamental principles that govern rates of reaction.

Rate of Reaction

As you can see from the above graph - either of the definitions can apply to rate and either would give you the same number. This is because the Change in Concentration (this is the difference between the starting concentration and the concentration at a fixed time after the reaction starts) of either the reactants or products should be relatively equal.

The graph also shows that as a reaction proceeds and the concentration of reactants decreases this would cause a change in rate as rate decreases over time as the concentration of reactants decreases

Collision Theory

In the above animation you can see how particles of a gas move at a constant temperature. Some of these particles are colliding in the animation to make something new - some of these particles are colliding and not reacting.

A collision which produces a new substance is called a successful collision

A collision which does not produce a new substance is an unsuccessful collision - an assumption of collision theory is that most particle collisions are unsuccessful.

As Rate of Reaction measures the change of reactants into products then rate of reaction measures the frequency of successful collisions. Any factor that can increase these collisions would therefore speed up rate and any factor that can decrease these collisions would slow the rate down.