# A 50 mL sample of 0.200 M sodium hydroxide is titrated with 0.200 M HCl. What is the initial pH?

Aug 22, 2016

$p H = 13.3$

#### Explanation:

It is well known that in aqueous solution, that

$p H + p O H = 14$

$p H = 14 - p O H$

$p O H = - {\log}_{10} \left[H {O}^{-}\right] = - {\log}_{10} \left(0.200\right)$ $=$ $0.70$

$14 - 0.70 = 13.3$

$p H$ should reasonably be high inasmuch as we measured it BEFORE the start of the titration. Given this, the information regarding the acid was a distractor. What will the $p H$ be when the $50.0 \cdot m L$ volume of $H C l$ is added?