Hess's Law Reaction Pathway Visualizer – AP Chemistry

Learning Objectives

Prove Enthalpy ($\Delta H$) is a state function independent of the reaction pathway.

Reverse sub-reactions and invert $\Delta H$ signs.

Multiply stoichiometric coefficients and scale $\Delta H$.

Cancel intermediates to form the target net equation.

Key Equations

$ \Delta H_{rxn} = \sum \Delta H_{\text{steps}} $

Reverse Eq: $ \Delta H_2 = -\Delta H_1 $

Multiply Eq by $n$: $ \Delta H_2 = n \Delta H_1 $

Why It Matters

Many reactions are too dangerous, too slow, or too complex to measure in a calorimeter. Hess's Law allows chemists to algebraically calculate the enthalpy change of a target reaction using known tabulated data steps.