| Date | May 2013 | Marks available | 1 | Reference code | 13M.3.sl.TZ2.C2 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Distinguish | Question number | C2 | Adapted from | N/A |
Question
Distinguish between a homogeneous and a heterogeneous catalyst.
Other than cost, state one advantage and one disadvantage of using a homogeneous catalyst rather than a heterogeneous catalyst.
Advantage:
Disadvantage:
Other than selectivity and cost, list three factors which should be considered when choosing a catalyst for a particular industrial process.
Markscheme
homogeneous catalyst is in the same phase/state as the reactants and heterogeneous is in a different phase/state to the reactants;
Advantage:
all catalyst exposed to reactants / does not depend on surface area / react more rapidly / OWTTE;
Disadvantage:
difficult to remove from products;
Accept “Cannot always be used at high temperature”.
Apply ECF if C2. (a) the wrong way round.
amount of reactant converted to product per amount of catalyst;
Accept efficiency / conversion rate.
ability to work under different/a range of conditions;
toxicity / environmental/health impact;
catalytic poisoning / active sites become blocked;
lifetime of catalyst;
ease of removal;
Examiners report
This question was relatively well tackled. Almost all knew the difference between the two types of catalysts, though many referred to “state” than the more correct “phase” and could not identify an advantage and a disadvantage and knew of at least some of the factors that need to be considered in decisions relating to the choice of a catalyst.
This question was relatively well tackled. Almost all knew the difference between the two types of catalysts, though many referred to “state” than the more correct “phase” and could not identify an advantage and a disadvantage and knew of at least some of the factors that need to be considered in decisions relating to the choice of a catalyst.
This question was relatively well tackled. Almost all knew the difference between the two types of catalysts, though many referred to “state” than the more correct “phase” and could not identify an advantage and a disadvantage and knew of at least some of the factors that need to be considered in decisions relating to the choice of a catalyst.
