Comparing rates

In a typical rates experiment, the mass or volume of product is measured at regular time intervals. The results are usually recorded in a table. For example:

Time / minVolume of gas produced / cm3
00
134
242
348
450
550

These results show that the reaction had finished by four minutes. No more gas was produced after that point.

However, the rate decreased during the reaction as the volume of gas produced decreased as the time increased.

Graphs

The rate of reaction can be analysed by plotting a graph of amount of product against time. The graph below shows this for two reactions.

Reaction rate graph – speed

Compared to the slow reaction, the graph line for the faster reaction:

  • has a steeper gradient at the start
  • becomes horizontal sooner (gas stops being produced sooner so the reaction finishes sooner) meaning that the rate of reaction is greater.