# What are carbonate ions and how can you recognize them?

Mar 27, 2017

Well, carbonate ions are represented by $C {O}_{3}^{2 -}$.

#### Explanation:

And how to demonstrate the presence of $C {O}_{3}^{2 -}$?

Well, you must acidify the solution, and collect the evolved carbon dioxide.

The reactions that occur here are (i):

$C {O}_{3}^{2 -} + 2 {H}^{+} \rightarrow C {O}_{2} \left(a q\right) + {H}_{2} O \left(l\right)$

And (ii):

$C {O}_{2} \left(a q\right) + C a {\left(O H\right)}_{2} \left(a q\right) \rightarrow C a C {O}_{3} \left(s\right) \downarrow + {H}_{2} O \left(l\right)$

Precipitation of calcium carbonate is not straightforwardly observed, and if you do this in the lab, it is a good idea to use authentic carbonates so that you know for what you are looking.

The alkaline earths (Group 2) form binary carbonates that are (reasonably) insoluble in water.