Given, the enthalpy of neutralization of the strong monobasic acid with a strong monoacidic base is −57.3 kJ/mol
Again, the enthalpy of neautralization of a weak monoprotic acid with a strong monoacidic base is −55.95 kJ/mol.
So the energy used for diisociation of week acid is (57.3−55.95) kJ/mol=1.35 kJ/mol
But, the heat required for complete ionization of weak monobasic acid is 1.4 kJ/mol
So the percentage ionization of the weak acid =1.4−1.351.4×100=3.571%