# What is the sf(OH^-) ion concentration in a solution of 0.0012M strontium hydroxide ?

$\left[O {H}^{-}\right] = 2.4 \times {10}^{- 3} \text{M}$
$S r {\left(O H\right)}_{2 \left(a q\right)}$ contains 2 moles of $O {H}^{-}$ ions so a solution that is $1.2 \times {10}^{- 3} \text{M}$ will have an $O {H}^{-}$ ion concentration which is equal to $1.2 \times {10}^{- 3} \times 2 = 2.4 \times {10}^{- 3} \text{M}$.