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CAIE IGCSE Chemistry 5.1.8 Enthalpy Change of a Reaction Using Questions

Calculate reaction enthalpy by summing bond energies absorbed in breaking bonds and released in forming bonds.

Syllabus
2026–2028
Course
Chemistry 0620

Exam points

  • calculate energy absorbed when bonds break
  • calculate energy released when bonds form
  • estimate enthalpy change from bond energies
  • identify bonds broken and formed in a reaction
  • use bond-energy data for combustion and addition reactions
  • compare calculated and observed energy changes
  • apply bond energies to unfamiliar molecules and equations

CAIE IGCSE Chemistry 5.1.8 Enthalpy Change of a Reaction Using Questions question 1

[Maximum number: 1]

The reaction between hydrogen and oxygen releases 486 kJ/mol486 \mathrm{~kJ} / \mathrm{mol} of energy.

2H2( g)+O2( g)→2H2O( g)2 \mathrm{H}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{~g})

The bond energy of H-H is 436 kJ/mol436 \mathrm{~kJ} / \mathrm{mol} and that of H-O is 464 kJ/mol464 \mathrm{~kJ} / \mathrm{mol}.
What is the bond energy of O=O ?

A

430 kJ/mol430 \mathrm{~kJ} / \mathrm{mol}

B

458 kJ/mol458 \mathrm{~kJ} / \mathrm{mol}

C

498 kJ/mol498 \mathrm{~kJ} / \mathrm{mol}

D

984 kJ/mol984 \mathrm{~kJ} / \mathrm{mol}

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