IB Chemistry SL 1.2.1 Bond energies
IB Chemistry SL 1.2.1 Bond energies
Practise bond enthalpy calculations by counting bonds broken and formed, then explain why these answers can differ from Hess's law values.
How this is tested
- calculate ΔH from bond enthalpies by counting exact bonds broken and formed, e.g. in ethanol combustion
- use bond data to find ΔH for reactions such as ethene hydration, CO + Cl2, or HBr addition to C=C
- explain why bond-enthalpy ΔH differs from Hess or ΔHf° values: averages for gaseous, not exact, species