# A certain solution has pH 3.89 at 0°C. What is the pOH and [OH^-]?

$p O H$ $=$ $14 - 3.89$ $=$ $10.11$
Given $p O H$, $\left[H {O}^{-}\right]$ $=$ ${10}^{- p O H}$ $=$ ${10}^{- 10.11}$ $m o l \cdot {L}^{-} 1$.
Note that in water, $p H + p O H = 14$ at $298 \cdot K$.