Cambridge AS & A Level Chemistry
5.1Enthalpy change, ΔH
Enthalpy change, ΔH in Cambridge AS & A Level Chemistry: what the syllabus expects you to know, the learning objectives and how to practise.
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Overview
Bond-energy calculations (5.1.4-5.1.6) are taught with Hess's law (5.2).
Learning objectives
What the syllabus expects you to be able to do.
- 5.1.1Recognise exothermic (negative ΔH) and endothermic (positive ΔH) changes.
- 5.1.2Construct and interpret reaction pathway diagrams showing ΔH and activation energy.
- 5.1.3Define standard conditions and the standard enthalpy changes of reaction, formation, combustion and neutralisation.
- 5.1.4Relate energy transfers to the breaking and making of bonds.
- 5.1.5Calculate enthalpy changes of reaction from bond energies.
- 5.1.6Recognise that some bond energies are exact and some are averages.
- 5.1.7Calculate enthalpy changes from experimental results using q = mcΔT and ΔH = −mcΔT/n.
Lessons
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Enthalpy changes and calorimetry
40 min
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Sample question
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