Question

When 1 mole of strong diprotic acid H₂A (completely ionised) is completely neutralized by NaOH then amount of heat is released is "E" KJ mol^–1. Calculate amount of heat released when one mole of weak monoprotic acid HB is completely neutralized by NaOH.
1. E
2. less than E/2
3. greater than E/2
4. None of these

Answer 1

Correct Answer - Option 2 : less than E/2

H₂A + 2NaOH → 2NaA + 2H₂O                       ΔH = E

(SA)      (SB) 

\(\mathop {HB}\limits_{(WA)}\) + NaOH → NaB + H₂O                            ΔH < \(\frac{E}{2}\)

HB is monoprotic & weak acid, so few amount of energy is required for its dissociation.