Distinguish between homogeneous and heterogeneous catalysts.

Discuss two factors which need to be considered when selecting a catalyst for a particular chemical process.

Identify the catalyst used in the catalytic cracking of long chain hydrocarbons and state one other condition needed.

State an equation for the catalytic cracking of the straight chain hydrocarbon pentadecane, \({{\text{C}}_{{\text{15}}}}{{\text{H}}_{{\text{32}}}}\), to produce two products with similar masses.

homogeneous catalysts are in the same phase/state as reactants and heterogeneous catalysts are in a different phase/state to reactants;

should produce only the desired product / selectivity;

efficiency;

should be able to work under both mild and severe conditions / should be able to work at high temperatures;

should not produce an (unwanted) environmental impact;

cost / economic viability / OWTTE;

ease of poisoning/contamination;

(catalyst a mixture of) silica/silicon dioxide/ \({\text{Si}}{{\text{O}}_2}\) and alumina/aluminium oxide/\({\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}\) / zeolites/aluminosilicates;

high temperature / 500 °C;

\({{\text{C}}_{15}}{{\text{H}}_{32}} \to {{\text{C}}_8}{{\text{H}}_{18}} + {{\text{C}}_7}{{\text{H}}_{14}}/{{\text{C}}_{15}}{{\text{H}}_{32}} \to {{\text{C}}_8}{{\text{H}}_{16}} + {{\text{C}}_7}{{\text{H}}_{16}}\);

Most candidates were aware of the differences between homogeneous and heterogeneous catalysts.

Few candidates could name the catalyst but knew one other condition needed for catalytic cracking.

Most correctly stated an equation for the catalytic cracking of pentadecane, but some added oxygen or water, and some had too many hydrogen atoms in the products.