Final answer:
After the reaction between Mg(NO3)2 and Na2CO3, 0 moles of Mg2+ ions are left in solution.
Step-by-step explanation:
To determine the number of moles of aqueous Mg2+ ions left in solution after adding 2.0 L of 1.0 M Na2CO3 to 1.0 L of 4.0 M Mg(NO3)2, we need to consider the reaction that occurs between Mg2+ and CO32- ions. The balanced equation for the reaction is:
Mg(NO3)2 + Na2CO3 → MgCO3 + 2NaNO3
From the balanced equation, we can see that 1 mole of Mg(NO3)2 reacts with 1 mole of Na2CO3 to produce 1 mole of MgCO3. Therefore, the number of moles of MgCO3 formed is equal to the number of moles of Mg2+ ions initially present in the solution.
Since the concentration of Mg(NO3)2 is 4.0 M and the volume is 1.0 L, the number of moles of Mg(NO3)2 is 4.0 moles. This means that there are initially 4.0 moles of Mg2+ ions in the solution.
After the reaction with Na2CO3, all the Mg2+ ions will react to form MgCO3. Therefore, there will be 0 moles of Mg2+ ions left in solution.