Question

The enthalpy of neutralization of a weak acid in $1M$ solution with a strong base is $-56.1kJmo{l}^{-1}$. If the enthalpy of ionization of the acid is $1.5kJmo{l}^{-1}$ and enthalpy of neutralization of the strong acid with a strong base is $-57.3kJequi{v}^{-1}$, what is % ionization of the weak acid in molar solution (assume the acid to be monobasic)?

• A. $10$
• B. $15$
• C. $20$
• D. $80$

Answer 1

Answer: (C)

$20$

Ideally, enthalpy of neutralization should be, $=-57.3$ $KJ/mol+$ $1.5$ $KJ/mol$

$=-55.8$ $KJ/mol$

Energy used for neutralization=$57.3-56.1$

$=1.2$ $KJ/mol$

$\therefore$ % ionization=$\frac{1.2}{1.5}\times 100$$=80$%

So, % of weak acid in solution=$20$%