If #Na_2S# is added to a solution containing #AgCl#, a black precipitate of #Ag_2S# forms. Why does this happen using Le Chateliers's principle?
The silver ion would combine readily with the sulfide
The production of
Consider the solubility expression that governs the solubility of the silver salts....
And this is certainly a measurable equilibrium, the which we express as
And so we know that the ion product is
On the other hand for
....the equilibrium quantity of silver ion in solution would precipitate out until it satisfied the solubility expression for silver sulfide.
If you are in second year you should work out the gram solubility of each silver salt under standard conditions....
Anyway back to old Le Chatelier's principle...you gots…
But because silver ion is REMOVED from the equilibrium, AS MIGHTILY insoluble silver sulfide, the equilibrium should move from right to left as we face the page. And so MORE silver chloride should dissolve, and silver ion reprecipitates as silver sulfide.