Question

The enthalpies of neutralisation of a strong acid HA and weaker acid HB by NaOH are -13.7 and -12.7 kcal/eq. When one equivalent of NaOH is added to a mixture containing 1 equivalent of HA and HB; the enthalpy change was -13.5kcal. In what ratio is the base distributed between HA and HB?

Answer 1

Let x equivalent of HA and y equivalent of HB are taken in the mixture

x + y = 1 ... (i)

x × 13.7 + y × 12.7 = 13.5 … (ii)

Solving eqs. (i) and (ii), we get 

x = 0.8, y = 0.2 

x: y = 4: 1