# What is the solubility product of calcium hydroxide?

The Ksp for calcium hydroxide is Ksp = $\left[C {a}^{2 +}\right] {\left[O {H}^{-}\right]}^{2}$
$C a O {H}_{2}$(s) -> $C {a}^{2 +}$ + 2$O {H}^{-}$
Solid substances are not included in writing an equilibrium expression. So you will only have the $C {a}^{2 +}$ and the $O {H}^{-}$ in the expression. The calcium ion has no exponent, the hydroxide ion must be squared because of the coefficient of 2.
The Ksp value for 4.68×10-6 for $C a O {H}_{2}$ indicates that this is a moderately soluble compound.