Calculate Enthalpy of Ionization of Weak Acid: ΔH3

[BayernBlues]

Homework Statement

Find the enthalpy of ionization of the weak acid, ΔH3

H3O+ + OH- <-> 2H2O....ΔH1
HA + OH- + H2O <-> A- + 2H2O...ΔH2
HA + H2O <-> H3O+ A-...ΔH3

The Attempt at a Solution

I won't show it here but I've found ΔH1 to be -52.33 kJ/mol and ΔH2 to be -5.21 kJ/mol. I don't know how to get the third enthalpy though, I know you'd use Hess' law but I don't really understand what to do here.

 

[Borek]

Obviusly you have to start with the second reaction, as it has HA and A^- in correct places. Then use the first reaction to get rid of OH^- on the LHS and H₂O on the RHS.