Both <u><em>soluble metal salt and carbon dioxide</em></u> may react with a base to form a solid or what we call a precipitate.
For instance when <u><em>carbon dioxide is bubbled through a solution of calcium hydroxide, it results to the formation or precipitate calcium carbonate.</em></u>
<em>Ca(OH)₂(aq) + CO₂(g) → CaCO₃(s) + H₂O(l)</em>
For the case of a soluble metal salt; an example is calcium nitrate, which is <em><u> a soluble metal salt, when reacted with a base like sodium hydroxide, it results to the formation of a solid calcium hydroxide</u></em> and sodium nitrate, a reaction called precipitation reaction.
