Spectator Ions?

Chemical equation writing......

Barium hydroxide and ammonium sulfate react to make an insoluble precipitate of barium sulfate, ammonia and water.

Ba(OH)2(aq) + (NH4)2SO4(aq) --> BaSO4(s) + 2NH3 + 2HOH(l)

It's tempting to write ammonium hydroxide, NH4OH as a product, but there is no molecular ammonium hydroxide in a solution labeled "ammonium hydroxide." There are small amounts of NH4+ and OH- present, just enough to make the solution slightly basic, but there is a great deal more NH3(aq) than there is NH4+.

NH3(aq) + HOH(l) <==> NH4+ + OH- ............... Kb = 1.8x10^-5
The small value of Kb indicates that the equilibrium lies far to the left and NH3 is the predominate species.

Back to the original chemical equation written correctly as an ionic equation:
Ba2+ + 2OH- + 2NH4^+ + SO4^2- --> BaSO4(s) + NH3(aq) + HOH(l)
No spectator ions.

It's unclear what your teacher may be expecting concerning NH4OH. If your teacher expects it to be ionized, then NH4+ and OH- ions are spectator ions. But if your teacher expects it to be "molecular" then there are no spectator ions. The problem is that your teacher shouldn't expect NH4OH at all.

======= Follow up =======

When reading Fooks's answer be sure you understand that there is no NH4OH in solution and it is NOT ionized to form NH4+ and OH- ions. Therefore, NH4+ and OH- CANNOT be spectator ions.

Ba(OH)₂(aq) + (NH₄)₂SO₄(aq) → BaSO₄(s) + 2NH₄OH(aq)

In the above equation, Ba(OH)₂(aq), (NH₄)₂SO₄(aq) and NH₄OH(aq) dissociate in aqueous solution to give mobile ions, but BaSO₄(s) cannot be written in ionic form. The ionic equation is :
Ba²⁺(aq) + 2OH⁻(aq) + 2NH₄⁺(aq) + SO₄²⁻(aq) → BaSO₄(s) + 2NH₄⁺(aq) + 2OH⁻(aq)

NH₄⁺ and OH⁻ ions are spectator ions because they do not change in the reaction.

This is a double replacement reaction. The spectator ions are the ions that did not form a precipitate. The (s) means BaSO4 is the precipitate. This means NH4+1 and OH-1 are the spectator ions

ions:Barium sulfate
covalent:errr...
ok, im confused

I agree with pisgahchemist's answer. However, . . .

You didn't write the equation and the expected answer may very well include the idea that NH4^+ and OH^- are the spectator ions. Check with your teacher on this point.

NH4+ and OH-