How can I calculate the enthalpy change of a reaction?

1 Answer
anor277
Jul 11, 2018

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....

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