# What is the pKa of buffer solution HC_2H_3O_2 when HCl is added?

## (HCl is part A) part B: What about when NaOH is added? (Google didn't tell me anything lol)

Jul 31, 2018

Look at the buffer equation....and we address $p H$ NOT $p {K}_{a}$, the which is the acid dissociation constant....$p {K}_{a}$ $H O A c = 4.76$.

#### Explanation:

A buffer is where a weak base, and its conjugate acid are mixed together in appreciable quantities to give a solution that resists gross changes in $p H$...and for such a system...

$p H = p {K}_{a} + {\log}_{10} \left\{\frac{\left[{A}^{-}\right]}{\left[H A\right]}\right\}$

In this scenario, where acetic acid is used as the acid...

$p H = 4.76 + {\log}_{10} \left\{\frac{\left[O A {c}^{-}\right]}{\left[H O A c\right]}\right\}$

Addition of acetic acid OR acetate ion (OR ${H}_{3} {O}^{+}$ or $H {O}^{-}$) should change the $p H$ of the solution only marginally. What will be the $p H$ of the buffer if [""^(-)OAc]=[HOAc]