Home Chemistry Thermodynamics and Thermochemistry Heat of Reaction The heat of neutralisation of HCl by NaOHis …
Chemistry Thermodynamics and Thermochemistry Heat of Reaction Single Correct MCQ
Published on: August 14, 2026

The heat of neutralisation of HCl by NaOHis – 55.9 kJ mol –1 . If the heat of neutralisation of HCN by NaOH is – 12.1 kJ/mol, the energy of dissociation of HCN is:

A
– 43.8 kJ
B
43.8 kJ
C
68 kJ
D
– 68 kJ

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Text Solution

Verified by Experts
The correct answer is:
B

Since neutralisation is an exothermic process, so the sign of its heat is

–ve. As we know, for weak acid, some amount of heat is used to dissociate it.

i.e, heat of dissociation (for weak acid) + heat of ionization = heat of ionization for strong acid with strong base, NaOH.

Heat of dissociation (for weak acid) + 12.1 = 55.9

∴ ∴ heat of dissociation (for weak acid) = 55.9 – 12.1 = 43.8 kJ

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