Question

The enthalpy of neutralization of a weak monoacidic base $\left(1M\right)$ with a strong acid is $-56.9kJ/mol$. If the enthalpy of ionization of a weak monoacidic base is $1.8$ $kJ/mol$ then the ionization of weak base in its molar solution is: (Given that $\Delta H_{neutralisation}$ of a strong acid and strong base $=-57.3KJ/mol$)

• A. $100/3$ %
• B. $200/3$ %
• C. $25$%
• D. None of these

Answer 1

The correct option is D None of these

The enthalpy of ionization of weak monoacidic base is $1.8kJ/mol$

$1.8kJ/mol\to 100$%

$\Delta H_{neutralisation}$ of a strong acid and strong base $=-57.3KJ/mol$
$\Delta H_{neutralisation}$ of a weak monoacidic base (1M) with a strong acid is $-56.9kJ/mol.$

Therefore, % of unionized weak monoacidic base:
$(57.3-56.9=0.4)\to \frac{100}{1.8}\times 0.4=\frac{200}{9}$%

So % ionization=$100-\frac{200}{9}=\frac{700}{9}$%

Option D is correct.