# The pH of water is a measure of what?

Feb 1, 2017

Of the concentration of the $\text{hydronium ion.........}$

#### Explanation:

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

Given the following equilibrium:

$2 {H}_{2} O \left(l\right) r i g h t \le f t h a r p \infty n s {H}_{3} {O}^{+} + H {O}^{-}$

${K}_{w} = \left[{H}_{3} {O}^{+}\right] \left[H {O}^{-}\right] = {10}^{-} 14$ at $298 \cdot K$

$p {K}_{w} = - {\log}_{10} \left[{H}_{3} {O}^{+}\right] - {\log}_{10} \left[H {O}^{-}\right] = - {\log}_{10} {10}^{-} 14$

$+ 14 = p H + p O H$

At neutrality, $\left[H {O}^{-}\right] = \left[{H}_{3} {O}^{+}\right]$, and $p H = p O H = 7.$