# Question #99100

Jan 14, 2017

Besides being an example of double replacement, this is a precipitation reaction, as calcium carbonate is not soluble in water, while the other compounds mentioned are.

#### Explanation:

The balanced equation is this:

${\left(N {H}_{4}\right)}_{2} C {O}_{3} \left(a q\right) + C a S {O}_{4} \left(a q\right) \rightarrow {\left(N {H}_{4}\right)}_{2} S {O}_{4} \left(a q\right) + C a C {O}_{3} \left(s\right) \downarrow$

The net ionic equation is

$C {a}^{2 +} + C {O}_{3}^{2 -} \rightarrow C a C {O}_{3} \left(s\right) \downarrow$

The spectator ions are $N {H}_{4}^{+}$ and $S {O}_{4}^{2 -}$

This reaction occurs because the combination of calcium ion and carbonate ion results in a compound of low solubility in water (calcium carbonate).