The absolute enthalpy of neutralisation of the reaction MgO(s)+2 HCl(a q) MgCl_2(a q)+H_2 O(l) will be

JIPMER 2007

Exam: JIPMER
Year: 2007
Subject: Chemistry
Chapter: Thermodynamics (C)

JIPMER 2007 · Chemistry · Thermodynamics (C)

The absolute enthalpy of neutralisation of the reaction MgO(s)+2...

The absolute enthalpy of neutralisation of the reaction

\mathrm{MgO}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{MgCl}_2(a q)+\mathrm{H}_2 \mathrm{O}(l)

will be

Options

Aless than $-57.33 \mathrm{~kJ} \mathrm{~mol}^{-1}$
B $-57.33 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Cgreater than- $57.33 \mathrm{~kJ} \mathrm{~mol}^{-1}$
D $57.33 \mathrm{~kJ} \mathrm{~mol}^{-1}$

Correct answer

A. less than $-57.33 \mathrm{~kJ} \mathrm{~mol}^{-1}$

Step-by-step solution

Heat of neutralisation of strong acid and strong base is

-57.33

kJ . MgO is weak base while HCI is strong acid, so the heat of neutralisation of MgO and HCI is lower to -57.33 kJ because MgO requires some heat in ionisation, then net released amount of heat is decreased.

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