Question

For the reaction Ag2S(s) ⇌ 2 Ag+ (aq) + S2- (aq), what happens to the equilibrium position if ammonium sulfate is added?

A) doubles

B) shifts to the left

C) does nothing

D) shifts to the right

E) halves

Answer 1

I don't think it will change the position at all although your prof may be expecting an answer of D. To make it shift to the left you must add Ag+ or S2- and neither is present in (NH4)2SO4. To shift to the right you must add something that reacts with either product but (NH4)2SO4 will do neither. Some may think adding (NH4)2SO4 will make it go to the right because of the formation of Ag2SO4; however, Ag2SO4 is more soluble than Ag2S (by far); for that reason the Ag2S solubility is the one that prevails.