Hess's law
Hess's law
Formula
ΔH_reaction = ΣΔH_steps
Real World
Engineers at BP use Hess cycles to calculate the enthalpy of partial oxidation reactions in oil refining that are too hazardous to measure directly in a lab.
Exam Focus
Draw the Hess cycle clearly; reverse a reaction's sign when flipping its direction, and show all working for full marks.
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