# If pH=7, what are [H_3O^+], and [HO^-]?

$\left[{H}_{3} {O}^{+}\right] = {10}^{-} 7 \cdot m o l \cdot {L}^{-} 1$.
By definition, $p H = - {\log}_{10} \left[{H}_{3} {O}^{+}\right]$.
And so if $p H = 7$, then $\left[{H}_{3} {O}^{+}\right] = {10}^{-} 7 \cdot m o l \cdot {L}^{-} 1$.
What is $\left[H {O}^{-}\right]$ in the given solution?