chem whatdriveschemicalreactions
Reactivity 1.2.4 - an application of Hess’s law uses enthalpy of formation data or enthalpy of combustion data to calculate the enthalpy change of a reaction
calculating enthalpy from standard enthalpy changes of combustion

general expression for standard enthalpy change of combustion
calculating enthalpy from standard enthalpy changes of formation

general expression for standard enthalpy change of formation