Catalyst: A catalyst provides an alternative reaction pathway for reaction with lower activation
energy. Catalyst regenerated/ not used up. Increases rate of reaction.

Enthalpy Profile Diagrams: Reactants and product should be shown at correct levels with respect
to each other. ∆H shown with arrow. Activation energy should be an upward arrow. Remember
axis and all labels.
• Two types of catalysts…
• Homogenous Catalysts: Has the same physical state as reactants. Two examples…
• Making Esters: Carboxylic acid + alcohol -> ester + water. Sulfuric acid H2SO4 as catalyst and
written above arrow. All of them are liquid.
• Ozone Depletion: 2O3 -> 3O2 Cl.
is catalyst. All of them are gases.
• Heterogeneous Catalysts: Has a different physical state from the reactants, name the substances
and their states. Usually solid. Reactant molecules are absorbed onto surface of catalyst, where
reaction takes place. After reaction, product leaves surface of catalyst by desorption.
• Examples: Making ammonia (Haber process) where Fe (s) is catalyst. Also hydrogenation of
alkenes where Ni (s) is catalyst.
• Sustainability and Catalysts: Use of catalyst is sustainable…
– Catalysts lower energy demand for reaction. Lower temperatures.
– Less combustion of fossil fuels so lower carbon dioxide emissions.
– Allows different reactions to take place with greater atom economy/ less waste.
• Some catalysts are toxic, be careful of disposal.