# Question 702e2

Aug 3, 2017

$\left[{\text{OH}}^{-}\right] = 5.6 \times {10}^{-} 12$ $M$

#### Explanation:

We're asked to find the hydroxide ion concentration $\left[{\text{OH}}^{-}\right]$ of a solution, given its $\text{pOH}$.

To do this, we can use the equation

"pOH" = -log["OH"^- ]

But rearrange it to solve for $\left[{\text{OH}}^{-}\right]$:

ul(["OH"^- ] = 10^(-"pOH")

We're given that $\text{pOH}$ $= 11.25$, so we have

["OH"^- ] = 10^(-11.25) = color(red)(ulbar(|stackrel(" ")(" "5.6xx10^-12color(white)(l)M" ")|)#

Since the $\text{pOH}$ has two decimal places, the hydroxide ion concentration has two significant figures.