Write the balanced chemical equation associated with the formation constant, 𝐾f , for each complex ion. Include phase symbols. AgI−2 : ↽−−⇀ Hg(NH3)2+4 : ↽−−⇀

Answer 1

These are two separate, unrelated complex ions, each needing its own equation. Nothing turns into anything else between them - your worksheet is just asking for two independent answers, and the formatting has run them together.

1. AgI₂^-

Ag⁺(aq) + 2 I^-(aq) ⇌ AgI₂^-(aq)

K_f = [AgI₂^-] / ([Ag⁺][I^-]²)

2. Hg(NH₃)₄²⁺

Hg²⁺(aq) + 4 NH₃(aq) ⇌ Hg(NH₃)₄²⁺(aq)

K_f = [Hg(NH₃)₄²⁺] / ([Hg²⁺][NH₃]⁴)

The pattern, so you can write any of these. A formation constant always describes the complex being built, so the free metal ion and the ligands go on the left and the complex on the right. Read the formula backwards to get your coefficients: the subscript on the ligand inside the complex is exactly how many of them you need. AgI₂^- has two iodides, so 2 I^-; Hg(NH₃)₄²⁺ has four ammonias, so 4 NH₃.

Check the charges balance, which also confirms you identified the metal's oxidation state correctly. Silver: (+1) + 2(-1) = -1, matching AgI₂^-. Mercury: (+2) + 4(0) = +2, matching Hg(NH₃)₄²⁺, and note that ammonia is a neutral ligand so it contributes nothing to the charge. If your charges do not balance, you have the wrong oxidation state on the metal, not a bad coefficient.

Two details the question specifically asks for. Phases: everything here is aqueous, including NH₃, since it is dissolved ammonia rather than the gas. Direction: write formation, not dissociation. The reverse reaction is perfectly real, but its constant is K_d = 1/K_f, and reversing the equation would give you the wrong quantity even though the chemistry is the same.