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CAIE A-Level Chemistry 8.3 Homogeneous and Heterogeneous Catalysts

Practise explaining catalysis through an alternative lower-EA mechanism, energy profiles and Boltzmann distributions.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • state that a catalyst provides a different mechanism with a lower activation energy
  • show the catalysed pathway with lower peak height but unchanged reactant, product and ΔH levels
  • use the larger Boltzmann area above the lower EA to explain the increased effective-collision frequency

Covered syllabus points

8.3.1—And use the terms catalyst and catalysis

8.3 Homogeneous and heterogeneous catalysts question 1

[Maximum number: 2]

Hydrogen halides are compounds formed when halogens (Group 17 elements) react with hydrogen. The bond polarity of the hydrogen halides decreases from HF to HI.

Some relevant data are shown in the table.

Table for Question 8.3 Homogeneous and heterogeneous catalysts question 1 — CAIE A-Level Chemistry AS

Hydrogen chloride undergoes a reversible reaction with oxygen.

4HCl( g)+O2( g)⇌2Cl2( g)+2H2O( g)4 \mathrm{HCl}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{Cl}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{~g})

The reaction is carried out at 400∘C400^{\circ} \mathrm{C} in the presence of a copper(II) chloride catalyst.

State the type of catalyst used in this reaction. Explain how a catalyst is able to increase the rate of a chemical reaction.

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