Catalysts

Catalyst definition

Substance that increases rate of reaction without being used up

How catalysts work

Lower activation energy so more particles have enough energy to react

Effect on collisions

Increases number of successful collisions

Effect on energy profile

Activation energy peak becomes lower

Effect on ΔH

No change to overall energy change of reaction

Biological catalysts

Enzymes

Enzyme property

Work best at specific temperature and pH

Catalyst reusability

Not consumed in reaction, can be used repeatedly

Catalyst specificity

Often only work for one specific reaction

Industrial catalysts

Reduce energy costs by allowing reactions at lower temperatures

Haber process catalyst

Iron

Contact process catalyst

Vanadium(V) oxide (V₂O₅)

Cracking catalyst

Aluminium oxide or silica

Hydrogenation catalyst

Nickel

Environmental benefit

Lower energy use → reduced CO₂ emissions

Heterogeneous catalyst

Catalyst in different physical state from reactants

Homogeneous catalyst

Catalyst in same physical state as reactants

Catalyst poisoning

Impurities block active sites and reduce effectiveness

Example of catalyst poisoning

Lead poisons catalytic converters

Key idea

Catalysts speed reactions by lowering activation energy, not by changing ΔH