[Hemidol]

(a) Write balanced molecular equations for the following potential precipitation reactions. Indicate
the states of reactants and products [(aq) or (s)].
(b) In those cases where a precipitate forms, write the net ionic equation. If there is no reaction, state
"No reaction."
(i) Na2S (aq) + Pb(NO3)2 (aq)  (ii) FeSO4 (aq) + Na3PO4 (aq)
(iii) MgCl2 (aq) + Pb(NO3)2 (aq)  (iv) K2SO4 (aq) + Ni(NO3)2 (aq) 


Here is my work for part a:

(i) Na2S(aq) + Pb(NO3)2(aq) -> 2 NaNO3(aq) + PbS(s)
(ii) 3 FeSO4(aq) + 2 Na3PO4(aq) -> Fe3(PO4)2(s) + 3 Na2SO4(aq)
(iii) MgCl2(aq) + Pb(NO3)2(aq) -> PbCl2(s) + Mg(NO3)2(aq)
(iv) K2SO4(aq) + Ni(NO3)2(aq) -> NiSO4(s) + 2 KNO3(aq)

Here is my work for part b:

(i) Pb²⁺(aq) + S^2-(aq) -> PbS(s)
(ii) 3 Fe²⁺(aq) + 2 PO4^2-(aq) -> Fe3(PO4)2(s)
(iii) Pb²⁺(aq) + 2 Cl^- -> PbCl2(s)
(iv) Ni²⁺(aq) + SO4^2-(aq) -> NiSO4(s)

How do these look? Any mistakes?

[plankk]

First three are correct. About fourth? Look for solubility of NiSO₄

[Hemidol]

First three are correct. About fourth? Look for solubility of NiSO₄

Ah, it's soluble. Nice find!

(iv) K2SO4(aq) + Ni(NO3)2(aq) -> NiSO4(aq) + 2 KNO3(aq)

Does that mean the net ionic equation must change to
(iv) Ni2+(aq) + SO42-(aq) -> NiSO4(aq)
Or should I just write "No reaction" (this is where my hunch is)

[plankk]

You should write "No reaction", because reaction doesn't occur. You dissolve only your salt.