# What are the equilibrium concentrations of the dissolved ions in a saturated solution of Fe(OH)_2 at 25°C?

Aug 3, 2017

We need ${K}_{\text{sp}}$ for $F e {\left(O H\right)}_{2}$.........

#### Explanation:

And we assess the equilibrium......

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

For which this site quotes ${K}_{\text{sp}} = 8 \times {10}^{-} 16$.

So we set the solubility of $F e {\left(O H\right)}_{2} \equiv S$.

And thus ${K}_{\text{sp}} = \left[F {e}^{2 +}\right] {\left[H {O}^{-}\right]}^{2} = S \times {\left(2 S\right)}^{2} = 4 {S}^{3}$

And thus......S=""^(3)sqrt((8.0xx10^-16)/4)

$= 5.85 \times {10}^{-} 6 \cdot m o l \cdot {L}^{-} 1$

And so $F {e}^{2 +} = 5.85 \times {10}^{-} 6 \cdot m o l \cdot {L}^{-} 1$

And $\left[H {O}^{-}\right] = 1.17 \times {10}^{-} 5 \cdot m o l \cdot {L}^{-} 1$

Can you work out the solubilities in $g \cdot {L}^{-} 1$?