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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Catalyst

A substance that speeds up a reaction by providing a pathway with a lower activation energy, and is not consumed. A small amount can be used again and again, replacing large quantities of stoichiometric reagents and saving energy.

Energy profile with and without a catalystEnergy against reaction progress. Reactants start higher than products. The uncatalysed path climbs a tall barrier; the catalysed path climbs a lower one (smaller activation energy) between the same reactants and products, so the reaction goes faster but releases the same overall energy.reaction progressenergyreactantsproductshigher Eₐlower Eₐuncatalysedcatalysed

The catalysed path has a lower energy barrier; the reactants and products are unchanged.

Example

In the Haber process an iron catalyst lets NX2\ce{N2} and HX2\ce{H2} combine to NHX3\ce{NH3} at a useful rate; the iron is not used up.

See alsoActivation energyGreen chemistry