Question

Which of the following reactions have maximum heat of neutralisation?

• A. $N{H}_{4}OHandC{H}_{3}OOH$
• B. $N{H}_{4}OHandHCl$
• C. $NaOHandC{H}_{3}OOH$
• D. $NaOHandHCl$

Answer 1

The correct option is D $NaOHandHCl$

More heat of neutralisation is generated between strong acid and strong base.
Since $NaOHandHCl$ are strong base and acid so this pair will produce maximum ${\Delta }_{neut}H$.


Theory :

Enthalpy of Ionization of Weak Electrolytes:

When a weak acid(or base) reacts with a strong base(or acid), the release of heat is < 57.1 kJ/mol.

Because these are not completely ionized in solutions. Some of the heat is consumed in ionizing. This heat is known as the Enthalpy of Ionization.

For example

$C{H}_{3}COOH+O{H}^{-}\to C{H}_{3}CO{O}^{-}+H_{2}O$ ${\Delta }_r{H}^o=-49kJ/mol$