Question

How can I calculate the enthalpy change of a reaction?

Answer 1

How else but by measurement...or by enthalpy summation....?

Explanation:

For say a combustion reaction....

`CH_4(g) + 2O_2(g) rarr CO_2(g) +2H_2O(l)`

`DeltaH_"rxn"^@=SigmaDeltaH_f^@""_"(products)"-SigmaDeltaH_f^@""_"(reactants)"`

`DeltaH_f^@` values are extensively tabulated...and these data are routinely available.

And so here we take the sum....

`{−393.5+2xx(-286.0)-(-74.9)}*kJ·mol^-1-=-890.6*kJ*mol^-1" (i.e. per mole of reaction as written...)"`

This site reports that the experimental value is `-890.5*kJ*mol^-1`, and as we would expect the calculated value using tabulated data is completely kosher....