CAIE IGCSE Chemistry 6.2.6 Rate changes using collision theory

Practise explaining rate changes with collision theory for temperature, pressure, concentration, surface area and catalysts.

Syllabus
2026–2028
Objective
6.2.6
Level
—

Exam points

  • explain temperature changes using kinetic energy, collision frequency and Ea
  • link higher concentration or pressure to more particles per unit volume and more collisions
  • explain powdered solids using greater surface area and increased collision frequency

6.2.6—Rate changes using collision theory question 1

[Maximum number: 3]

The Periodic Table is a method of classifying elements.

PCl3\mathrm{PCl}_{3} reacts with chlorine, Cl2\mathrm{Cl}_{2}, to form PCl5\mathrm{PCl}_{5}. This reaction is exothermic and reaches an equilibrium.

PCl3( g)+Cl2( g)⇌PCl5( g)\mathrm{PCl}_{3}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{PCl}_{5}(\mathrm{~g})

Explain, in terms of particles, what happens to the rate of the forward reaction when the reaction mixture is heated.

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