art 3: Formation of sulfide precipitates Metal sulfides are usually insoluble (n

Question

art 3: Formation of sulfide precipitates Metal sulfides are usually insoluble (note the Ksp values in the appendix). However, metal sulfides have extremely low Ksp values, while others are somewhat more oluble. This fact can be utilized in separation schemes. The solubility of these sulfides s also strongly influenced by pH. In this section, you will test the solubility of your ations with sulfide under both basic and acidic conditions. ome n order to produce the sulfide anion, we will add thioacetamide, CH3CSNH2, to hot vater. This sulfur-containing molecule undergoes an equilibrium reaction to produce mall amounts of hydrogen sulfide. As this reaction is endothermic, warming the water vill drive the reaction to the right (Le Châtelier again!),. CH3CSNH2 (aq) + 2 H2O (I)# CH3C02-(aq) + NH4+(aq) + H2S (aq) lydrogen sulfide is in turn a weak diprotic acid. As such, aqueous H2S solutions will ontain a small amount of the sulfide anion. HaS (aq) + 2 H2O (l) 2 H30+(aq) + S2-(aq) The concentration of sulfide anions varies with the solution pH. Carefully explain this bservation, including the role of Le Châtelier's principle. Do you expect the sulfide oncentration to be highest at low, high, or neutral pH? Why?

Explanation / Answer

The ionization of sulfide ions in water is given by

H2S(aq) + 2H2O(l) == 2H3O+(aq) + S2-(aq)

According to Lechatiliers principles addition of reactants and removal products shifts the reaction towards right side(forward direction)

Addition of products and removal of reactants shifts the reaction left side(backward direction)

Thus, if pH of solution decreases by increasing the concentration of H+ ions in solution the reaction shifts to backward due to increase in H3O+ species

If the pH of solution increases by removing H3O+ ions then the reaction shifts to forward and the sulfide ion concentration will increases

Therefore, high pH increases the concentration of sulfide ions in solution

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.