# Question 38d7f

Apr 14, 2016

${\text{Mg"_ ((aq))^(2+) + "CO"_ (3(aq))^(2-) -> "MgCO}}_{3 \left(s\right)}$

#### Explanation:

You're mixing magnesium nitrate, "Mg"("NO"_3)_2, and sodium carbonate, ${\text{Na"_2"CO}}_{3}$, two soluble ionic compounds that dissociate completely in aqueous solution to form cations and anions.

You can thus represent the two reactants as

${\text{Mg"("NO"_ 3)_ (2(aq)) -> "Mg"_ ((aq))^(2+) + 2"NO}}_{3 \left(a q\right)}^{-}$

${\text{Na"_ 2"CO"_ (3(aq)) -> 2"Na"_ ((aq))^(+) + "CO}}_{3 \left(a q\right)}^{2 -}$

Notice that the reaction produces magnesium carbonate, ${\text{MgCO}}_{3}$, an insoluble solid that precipitates out of solution, and aqueous sodium nitrate, ${\text{NaNO}}_{3}$, which will exist as sodium cations and nitrate anions in solution.

This means that you can rewrite the balanced chemical equation that describes this double replacement reaction like this

"Mg"_ ((aq))^(2+) + 2"NO"_ (3(aq))^(-) + 2"Na"_ ((aq))^(+) + "CO"_ (3(aq))^(2-) -> "MgCO"_ (3(s)) darr + 2 xx ["Na"_ ((aq))^(+) + "NO"_(3(aq))^(-)]

This represents the complete ionic equation. To get the net ionic equation, you need to remove spectator ions, i.e. ions that are present on both sides of the equation.

"Mg"_ ((aq))^(2+) + color(red)(cancel(color(black)(2"NO"_ (3(aq))^(-)))) + color(red)(cancel(color(black)(2"Na"_ ((aq))^(+)))) + "CO"_ (3(aq))^(2-) -> "MgCO"_ (3(s)) darr + color(red)(cancel(color(black)(2"Na"_ ((aq))^(+)))) + color(red)(cancel(color(black)(2"NO"_ (3(aq))^(-))))#
$\textcolor{g r e e n}{| \overline{\underline{\textcolor{w h i t e}{\frac{a}{a}} \textcolor{b l a c k}{{\text{Mg"_ ((aq))^(2+) + "CO"_ (3(aq))^(2-) -> "MgCO}}_{3 \left(s\right)} \downarrow} \textcolor{w h i t e}{\frac{a}{a}} |}}}$ 