如何计算Hess's Law

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Hess's Law states that the total enthalpy change of a reaction is independent of the pathway taken — it depends only on the initial and final states. This allows calculation of ΔH for reactions that are difficult to measure directly.

分步指南

1. 1Write the target reaction
2. 2Identify a series of known reactions that sum to the target
3. 3Reverse any reaction that needs to be reversed (change sign of ΔH)
4. 4Multiply reactions by appropriate stoichiometric factors
5. 5Sum all ΔH values

例题解析