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CAIE IGCSE Chemistry Activation Energy Definition

Practise defining activation energy as the minimum energy required for colliding particles to react and identifying it on a reaction pathway.

Syllabus
2026–2028
Course
Chemistry 0620

Exam points

  • define activation energy as the minimum energy colliding particles must have to react
  • identify activation energy as the energy rise from reactants to the top of the pathway barrier

5.1.5—Activation energy, Ea, as the minimum question 1

[Maximum number: 1]

The chemical equation for the complete combustion of ethanol, C2H5OH\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}, is shown.

C2H5OH+3O2→2CO2+3H2O\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+3 \mathrm{O}_{2} \rightarrow 2 \mathrm{CO}_{2}+3 \mathrm{H}_{2} \mathrm{O}

The energy released when one mole of ethanol undergoes complete combustion is 1280 kJ .
Part of the energy level diagram for this reaction is shown.

Figure for Question 5.1.5—Activation energy, Ea, as the minimum question 1 — CAIE IGCSE Chemistry

What does X represent?

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