10.2 Catalysts

Substance that changes rate of reaction without undergoing any permanent change itself

Not used up in a chemical reaction May react with a reactant to form an intermediate or could provide a surface for the reaction to take place At the end of the reaction, catalyst is regenerated

Provide an alternative reaction pathway of lower activation energy

Reactants have greater energy than products

Products have greater enthalpy than the reactants

Homogeneous catalysts Heterogeneous catalysts

It has the same physical state as the reactants Catalyst reacts with reactants to form an intermediate Intermediate breaks down to give product and regenerates the catalyst

Making esters with sulfuric acid (all are liquids) Ozone depletion with Cl radicals as catalysts (gases)

It has a different physical state from the reactants Usually solids in contact with gaseous reactants or reactants in solution.

Reactant molecules are adsorbed (weakly bonded) onto the surface of the catalyst, where reaction takes place After reaction, the product molecules leave the surface of the catalyst by desorption

Haber process Reforming Hydrogenation of alkenes Contact process

Fe (s)

Pt (s) Rh (s)

Ni (s)

V2O5 (s)

Contain catalyst made of platinum, rhodium and palladium Honeycomb mesh gives large surface area Harmful gases from combustion are converted into less harmful ones Carbon monoxide is oxidised to carbon dioxide Nitrogen monoxide is reduced to nitrogen gas

Lower activation energy Reduce temperature and energy needs for process Less electricity and fossil fuels used Cut costs and increase profitability