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How can I calculate the enthalpy change of a reaction?

Answer 1

Naomi Aronson

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

For instance, in a combustion process...

#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.

So let's take the total here.

#{−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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Answer 2

Mateo Aguilar

You can calculate the enthalpy change of a reaction using the equation: ΔH = ΣH(products) - ΣH reactants.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.