Question

How would you balance a reaction with a polyatomic ion only on one side?

Example would be having ammonium `(NH_4)_2` on one side and then having nitrogen `N_2` + water `H_2O` on the other side. Would you balance each individual atom, being that the polyatomic ion is only on one side?

Answer 1

Yes, balance each individual atom.

It doesn't matter that you have a polyatomic ion on one side; you only need to worry about the conservation of mass, which will ultimately pertain to the number of atoms, regardless of the molecule in which they reside or don't reside.

If we hypothetically had this reaction for simplicity (which of course isn't real or realistic):

`("NH"_4)_2"O" -> "N"_2 + "H"_2 + "O"_2`

then we would balance it like so:

`2("NH"_4)_2"O" -> 2"N"_2 + 8"H"_2 + "O"_2`

You can convince yourself that there are on each side:

• four `"N"`
• sixteen `"H"`
• two `"O"`