A couple of ionic equations

[A5HLEY]

Ok, so I need to formulate the ionic equation that forms when Na₂CO₃ and MgSO₄ are combined. I have several choices to choose from, as follows I'll put charges in parenthesis):


a). 2Na(+)(aq) + CO₃(2-)(aq) + Mg(2+)(aq) + SO₄(2-)(aq) --> MgCO₃(s) + 2Na(+)(aq) + SO₄(2-)(aq)

b). Na(2+)(aq) + CO₃(2-)(aq) + Mg(2+)(aq) + SO₄(2-)(aq) --> MgCO₃(s) + Na(+2)(aq) + SO₄(2-)(aq)

c). Na(2+)(aq) + CO₃(2-)(aq) + 2Mg(+)(aq) + SO₄(2-)(aq) --> MgCO₃(s) + Na(+2)(aq) + SO₄(2-)(aq)

d). CO₃(2-)(aq) + Mg(2+)(aq) + SO₄(2-)(aq) --> MgCO₃(s) + SO₄(2-)(aq)

I really don't understand how to decide which one it is. And also, how do you write a net ionic equation from the one you choose? I know you have to consider spectator ions (which I know remain the same throughout the reaction), but I'm not sure how to determine which are the spectators.

Any input would be wonderful!

[peter]

First you write a balanced equation of the reaction:

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Na2CO3 + MgSO4 = MgCO3 + Na2SO4

Then decompose all solvable compounds to ions and write ionic equation:

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2Na{+}(aq) + CO3{2-}(aq) + Mg{2+}(aq) + SO4{2-}(aq) = MgCO3(s) + 2Na{+}(aq) + SO4{2-}(aq)

which is answer a)
Hope that helps

Peter.

[paully]

peter is right ashley but what he didnt tell you is that the spectator ions are the ones that you said, the ones that stay the same through the reaction. Magnesium changes from an aqueious to a soild because magnesium carbonate is insoluble

(the solubilities of corbonate, nitrates, sulfates etc are written on the back of your chemical equation sheet that you get to use in all tests)

but the sodium stays aqueious because sulfate is soluble