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CAIE AS Chemistry 8.2.3 Temperature and Reaction Rate

Practise explaining a temperature-rate change through the energy distribution and frequency of effective collisions, linking Boltzmann distributions to activation energy.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • state that increasing temperature increases the proportion of particles with energy equal to or above EA
  • link this larger energetic fraction to more effective collisions per unit time and a faster reaction
  • avoid claiming that EA changes with temperature or that every collision becomes successful

8.2.3—In terms both of the Boltzmann distribution question 1

[Maximum number: 2]

Calcium, magnesium and radium are Group 2 elements. Radium follows the same trends as the other members of Group 2.

Cold water reacts slowly with a piece of Mg to produce bubbles of H2( g)\mathrm{H}_{2}(\mathrm{~g}). Cold water reacts rapidly with burning Mg to produce H2( g)\mathrm{H}_{2}(\mathrm{~g}) in an explosive mixture.

Mg+2H2O→Mg(OH)2+H2\mathrm{Mg}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{Mg}(\mathrm{OH})_{2}+\mathrm{H}_{2}

Explain why the rate of reaction of cold water with burning magnesium is greater.

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