(the two possible sequences share the same initial state and the same final state), the change in
enthalpy will be the same.
Example: Given the following thermochemical equations:Solution: Equations a, b, and c must be combined to obtain equation d. Since equation d contains only C, H 2 , and C 3 H 8 , we
must eliminate O 2 , CO 2 , and H 2 O from the first three equations. Equation a is reversed to get C 3 H 8 on the product side.e)(Note that when we reverse the reaction, the sign of the enthalpy change is reversed as well.)Next, equation b is multiplied by 3 (this gives equation f) and c by 4 (this gives equation g). The following addition is
done to obtain the required equation d: 3b + 4c + e.f)a)b)Calculate ΔH for the reaction:c)d) 3C (graphite) + 4H 2 (g) → C 3 H 8 (g)