Why is Calcium Hydroxide “relatively insoluble”? I mixed NaOH(aq) and CaCl2(aq) and somehow there’s precipitate, despite the fact that calcium in OH is said to be soluble.
1 Answer
May 29, 2018
"Soluble" versus "insoluble" is not as clearly defined as you might think from just looking at "solubility rules".
Explanation:
There is no real break between "soluble" and "insoluble" materials. Rather, there is a continuous range of solubilities from obviously soluble compounds like sodium chloride to essentially insoluble ones like mercury sulfide. In between are a lot of things for which solubility is relative.
Calcium hydroxide is among those in-between compounds. It is more soluble than most metal hydroxides, but its solubility still only about a gram per liter. So unless your reactants are quite dilute you should expect to get some calcium hydroxide precipitate.
