Rate of reaction is a measure of how fast a reaction takes place. In industry, chemists control rates of reaction to ensure the production is safe but still fast enough to keep up with demand.

The rate of reaction can change during the course of a reaction. The average rate of reaction can be calculated using:

- data from a table of results, or
- values from a graph

To find out the average rate of reaction at 20 seconds:

= 2 cm^{3}/s

- Question
During a reaction between hydrochloric acid and calcium carbonate, it takes 20 seconds to collect 80 cm

^{3}of carbon dioxide.What is the average rate of reaction over this time?

The average rate of reaction

= 4 cm

^{3}/s

The rate of reaction at a specific time is equal to the gradient of the graph at that time - it is equal to the gradient of the tangent.

Rate of reaction at 20 seconds

= gradient of tangent

=

= 3 cm^{3}/s