Chemistry question

Question

"Silver chloride is soluble in concentrated ammonia forming the complex diamminesilver(I) ion complex, [Ag(NH₃)₂]⁺. If the solution containing the complex ion is acidified, silver chloride precipitates. Explain why supporting your answer with the appropriate chemical equations."

Answer 1

AgCl(s) + 2NH₃(aq) ==> [Ag(NH₃)₂]⁺_(aq) + Cl^-(aq) ... equation for formation of complex

Ag⁺(aq) + 2NH₃(aq) ==> [Ag(NH₃)₂]⁺(aq) ... net equation for formation of complex

Ammonia increases solubility of AgCl because it essential removes Ag⁺ from solution (see net equation) and according to Le Chatelier, this pulls reaction to the product side, thus increasing solubility of AgCl(s).

Here, Ag⁺ is acting as a Lewis acid and NH₃ is acting as a Lewis base.

When the complex ion [Ag(NH₃)₂]⁺ is acidified, the complex is destroyed, and the Ag⁺ precipitates again as AgCl(s).

[Ag(NH₃)₂]⁺(aq) + Cl^-(aq) + 2H⁺(aq) ==> AgCl(s) + 2NH₄⁺(aq) ... precipitation in presence of H⁺