Chapter 13, Problem 148QP

Consider a buffer solution prepared by adding equal moles of the acid $\text{HOCl}$ and an ionic compound that contains its conjugate base, $\text{NaOCl}\text{.}$ The resulting equilibrium occurring in this solution is:

$\text{HOCl}(aq)+{\text{H}}_2\text{O}(l)\rightleftharpoons {\text{OCl}}^{-}(aq)+{\text{H}}_3{\text{O}}^{+}(aq)$

Given that the pH of this solution is $7.4,$ how would the $\text{pH}$ of this solution change when $0.10$ mol $\text{HCl}$ is added to $1.00L$ of this solution?

A. The pH would increase to $\mathrm{13.00.}$

B. The pH would decrease to $\mathrm{1.00.}$

C. The pH would increase by less than $1.00$ pH unit.

D. The pH would decrease by less than $1.00$ pH unit.

E. The pH would not change at all.

How would the pH change if the $\text{HOCl and NaOCl}$ were not in the solution when the $\text{HCl}$ was added?