The heat of ionization of weak acid and a weak base are 'x' and 'y' k.cals. Then the heat of neutralization of that weak acid and weak base in K.cal:

The reaction of dissociation of weak acid is given as:

$\mathrm{Weak}\text{ acid }\to {\text{ H}}^{+}$ 

The enthalpy for this reaction is x.

 The reaction of dissociation of weak base is given as:

$\mathrm{Weak} \mathrm{base} \to {\mathrm{OH}}^{-}$ 

The enthalpy for this reaction is y.

Adding both the reaction, we get:

${\text{Weak acid + weak base → H}}^{+}+{\mathrm{OH}}^{-}$ 

Enthalpy will be = x + y

Since, it is an neutralization reaction, the heat evolved will be = -13.7 k.cal.

So, the total enthalpy will be:

$=-13.7+(x+y)$

Therefore, the correct option is C.