# Question 17d18

May 22, 2017

$1.2 \times {10}^{-} 10 M$

#### Explanation:

We're trying to find the $\left[{H}_{3} {O}^{+}\right]$ of a solution with a given $p O H$.

We know that $p H$ and the $p O H$ must add up to $14.00$:

$p H + p O H = 14.00$

and the relationship between $p H$ and the $\left[{H}_{3} {O}^{+}\right]$ is

$\left[{H}_{3} {O}^{+}\right] = {10}^{- p H}$

Thus,

$p H = 14.00 - 4.07 = 9.93$

[H_3O^+] = 10^(-9.93) = color(red)(1.2 xx 10^-10 M#