as long as the initial and final conditions are the same, the enthalpy change for any reaction should be the same, regardless of route taken.
summary??
when there is more than 1 way that the final product can be made, the enthalpy change that occurs when reactants convert to products should be the same whichever route is used to make them.
why can't the enthalpy change be calculated for some reactions?
may apply for reactions involving reactants that are only solids or gases and for which the temp change can't be measured.
how can we use Hess' Law?
we can calculate the enthalpy change with a theoretical value using the enthalpy change values for an alternate route.
