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CAIE IGCSE Chemistry 6.2.5 Collision theory in terms of: (a)

CAIE IGCSE Chemistry 6.2.5 Collision theory in terms of: (a)
Cambridge IGCSE Chemistry 0620 syllabus for exams in 2026, 2027 and 20282026–2028

Practise using collision theory to link particle concentration, collision frequency, kinetic energy and activation energy to rate.

How this is tested

  • distinguish concentration effects from temperature effects on collision energy
  • link falling concentration to fewer successful collisions as a reaction proceeds

Question 14

[Maximum number: 1]

The reaction between two aqueous compounds, X and Y, is slow and exothermic.
The graph shows how the rate of this reaction changes with time.

Figure for Question 14 — CAIE IGCSE Chemistry

A student suggests that the rate of reaction decreases with time because:
1 the activation energy decreases
2 the speed of the molecules of X and Y decreases
3 the concentration of both X and Y decreases with time.

Which suggestions are correct?

A

1 and 2

B

1 and 3

C

2 only

D

3 only