# Why does calcium oxide give rise to TWO equiv of hydroxide ion in aqueous solution?

${O}^{2 -} + {H}_{2} O \left(l\right) \rightarrow 2 H {O}^{-}$...
$C a O \left(s\right) + {H}_{2} O \left(l\right) \rightarrow C a {\left(O H\right)}_{2} \left(s\right)$