Heat of Neutralization-

The amount of heat evolved when 1g equivalent of an acid is neutralized by base. 

H⁺ + OH⁺ à H₂O                 ΔH = -57.1 Kj/mol

     1mol    1mol

H₂SO₄ ---> 2H⁺ + SO₄^2-

(1 mol)

98g – 49g is 1 gram equivalent bco₃ we want 1Hydrogen ion

1 gram equivalent of dibasic or tri basic acid produced 1 mole of H⁺ ions & therefore 1grame equivalent of acid is taken.

Heat of neutralization of weak acid or weak base is always less than that strong acid or strong base.

NH₄OH + HCL → NH₄CL + H₂O                          ΔH = -54.1 KJ/mol, 3 KJ is used

 NH₄OH + CH₃COOH → CH₃COO NH₄ + H₂O     ΔH = -51 in dissociation

Heat of neutralization is less bco₃ some amount of energy is utilized to dissociate weak base & weak acid.

Therefore heat of neutralization is always less than that of -57.1s