Final answer:
The balanced net ionic equation for the precipitation of MgCO3 when aqueous solutions of Na2CO3 and Mg(NO3)2 are mixed is Mg2+(aq) + 2CO3²-(aq) -> MgCO3(s).
Step-by-step explanation:
The balanced net ionic equation for the precipitation of MgCO3 when aqueous solutions of Na2CO3 and Mg(NO3)2 are mixed is:
Mg2+(aq) + 2CO3²-(aq) -> MgCO3(s)
In this reaction, the sodium ion (Na+) and the nitrate ion (NO3-) are spectator ions, meaning they are present on both sides of the equation and do not participate in the reaction. The net ionic equation only includes the species directly involved in the formation of the precipitate.