After the addition of 6 M HCl, H₂S and 0.2 M HCl, OH⁻ to a pH of 8, and (NH4)2HPO₄ with NH₃, which of the following ions will be soluble?
1) Mg²⁺
2) NH₄⁺
3) S2-
4) OH⁻
5) PO₄³⁻