A catalyst is a substance that increases the rate of reaction, but can be recovered, unchanged at the end.
Only a very small mass of catalyst is needed to increase the rate of a reaction. However, not all reactions have suitable catalysts.
Different substances catalyse different reactions. The table describes three common catalysts.
|Iron||The Haber process (making ammonia)|
|Vanadium (V) oxide||The contact process (a stage in making sulfuric acid)|
|Manganese dioxide||Decomposition of hydrogen peroxide (produces water and oxygen)|
A catalyst provides an alternative reaction pathway that has a lower activation energy than the uncatalysed reaction. This does not change the rate of collisions. However, it does increase the rate of successful collisions because a greater proportion of collisions now exceeds this lower activation energy.
Some enzymes can be adapted or made for use in industry. The conditions that the enzymes work in is limited but this can bring benefits. For example, the use of enzymes allows some industrial reactions to happen at lower temperatures and pressures than traditionally needed. This helps to reduce energy demands.
Enzymes are used in everyday products such as washing powders, where they break down food stains.