The absolute enthalpy of neutralisation of the reaction
MgO(s) + 2HCl(aq) → MgCl₂(aq) + H₂O(l) will be

Options

(a) -57.33 kJ mol⁻¹
(b) greater then -57.33 kJ mol⁻¹
(c) less then -57.33 kJ mol⁻¹
(d) 57.33 kJ mol⁻¹

Correct Answer:

less then -57.33 kJ mol⁻¹

Explanation:

MgO is the oxide of weak base and we know that heat of neutralisation of 1 eq. of strong acid with strong base is -57.33 kJ/mol.
⇒ With weak base some heat is absorbed in dissociation of weak base.
⇒ Heat of neutralisation of weak base with strong acid will be – 57.33 kJ/mol.