Question

How can we find `DeltaH_"rxn"^@` for...? `NaOH(s) + HCl(g) rarr NaCl(s) + H_2O(l)`?

Answer 1

You normally would quote INDIVIDUAL `DeltaH_f^@` for reactants and products.

I get `DeltaH_"rxn"^@=-134.7*kJ*mol^-1.`

Explanation:

But, we can find `DeltaH_f^@` for the participating species on the [interwebz.....](https://en.wikipedia.org/wiki/Standard_enthalpy_of_formation) :

`NaOH(s) + HCl(g) rarr NaCl(s) + H_2O(g)`

And the various `DeltaH_f^@` are taken from the given site.

`NaOH(s),` `DeltaH_f^@=-426.0*kJ*mol^-1`

`NaCl(s),` `DeltaH_f^@=-411.2*kJ*mol^-1`

`HCl(g),` `DeltaH_f^@=-92.3*kJ*mol^-1`

`H_2O(g),` `DeltaH_f^@=-241.8*kJ*mol^-1`

Now `DeltaH_"rxn"^@=SigmaDeltaH_f^@"products"-SigmaDeltaH_f^@"reactants"`

`{(-241.8-411.2)-(-426.0-92.3)}*kJ*mol^-1=-134.7*kJ*mol^-1`

If I were you, I would check on the `DeltaH_f^@` values. All care taken, but no responsibility admitted.......