# Question & Answer: The Acid-insoluble sulfides and Base-insoluble sulfides can be separated from each other by…..

The Acid-insoluble sulfides and Base-insoluble sulfides can be separated from each other by changing the pH of the aqueous solution that contains them. At low pHs the Acid-insoluble sulfides will precipitate out. What role does the acid play in this process?

 The H+ ion is produced by the dissolving sulfide, so the presence of an acid hinders the dissolution process. The sulfide reacts with the H+ ion, forming the cation and H2S. The sulfide reacts with any OH– ions present forming S(OH)2 and the cation. The sulfide forms a complex ion with the H+ provided by the acid. The acid does not play a role in the dissolution process of metal sulfides.

The H+ ion is produced by the dissolving sulfide, so the presence of an acid hinders the dissolution process.

Don't use plagiarized sources. Get Your Custom Essay on
Question & Answer: The Acid-insoluble sulfides and Base-insoluble sulfides can be separated from each other by…..
GET AN ESSAY WRITTEN FOR YOU FROM AS LOW AS \$13/PAGE

The dissolved molecular hydrogen sulfide dissociates into hydrogen ions, hydrogen sulfide ions, HS , and sulfide ions, S2-. Three equilibria are involved:

H2S(g) $\rightleftharpoons$ H2S(aq)

H2S(aq) $\rightleftharpoons$ H++ HS K1 = [ H+] [HS] / [H2S] = 5.7×10−8

HS$\rightleftharpoons$ H+ + S2- K2 = [ H+]2 [ S2−] / [ HS] =1×10 −1 9

The low value of K2 suggests that there is very little free S2- in aqueous solutions unless they are extremely basic.

Therefore, the precipitation of metal sulfides is best written

M2+ + H2S MS(s) + 2H+