Enthalpy is an extensive property. In general, if enthalpy of an overall reaction AB along one route is rH and rH1, rH2, rH3... represent enthalpies of intermediate reactions leading to product B. What will be the relation between rH overall reaction and rH1, rH2.... etc for intermediate reactions.


In general, if enthalpy of an overall reaction AB along one route is rH and rH1, rH2, rH3...... representing enthalpies of reaction leading to same product B along another route, then we have
rH=rH1+rH2+rH3.........