Can (SO4)2 be alone as a reactant? Thanks!?

Question

Can (SO4)2 be alone as a reactant like below:

Al3 + 3 NH4 + 3 (SO4)2 = 3 AlNH4(SO4)2

I would greatly appreciate any help.

Answer 1

Interesting question. SO4 and NH4 do not (normally) occur on their own, but only as ions, SO4 2- and NH4+ respectively.

AlNH4(SO4)2 is an ionic compound, containing Al3+, NH4+, and SO4 2-.

So when the compound is being made by crystallisation from a solution that contains these ions, the correct equation is

Al 3+ + NH4+ + 2 SO4 2- = AlNH4(SO4)2

And you can see that the equation is balanced correctly for charges, as well as for all the atoms. By the way, this salt actually contains 12 molecules of water of crystallisation, so what really happens is

Al 3+ + NH4+ + 2 SO4 2- + 12 H2O = AlNH4(SO4)2.12H2O

Hope this helps.