6.6—Hess’s Law

Know Hess’s Law and be able to apply it to: i constructing enthalpy cycles ii calculating enthalpy changes of reaction using data provided, or data selected from a table or obtained from experiments.

Use —hess’s law to connect the rule to the data and decision in the question.

This matters because —hess’s law determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —hess’s law to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Hess’s Law is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.