Problem 7 - Chemistry

Question

Which is more likely to dissolve in an acidic solution, silver sulfide or silver chloride? Why?

Step-by-Step Solution

Answer

Silver sulfide (Ag2S) is more likely to dissolve in an acidic solution because, in acidic environments, sulfide ions combine with H⁺ ions to form H2S gas, decreasing the concentration of S²⁻ ions and allowing more Ag2S to dissolve, while silver chloride (AgCl) does not react with H⁺ ions and its dissolution remains unaffected.

Step 1: Write down the solubility equilibria for silver sulfide and silver chloride

First, let's write down the solubility equilibrium reactions for each compound. For silver sulfide (Ag2S): \[Ag2S(s) \rightleftharpoons 2Ag^+(aq) + S^{2-}(aq)\] For silver chloride (AgCl): \[AgCl(s) \rightleftharpoons Ag^{+}(aq) + Cl^{-}(aq)\]

Step 2: Study the behavior of each compound in acidic environments

Now, let's study how each compound behaves in acidic environments by writing the reaction equation of the respective anions with H+ ions: For sulfide ion (S²⁻): \[S^{2-}(aq) + H^+(aq) \rightleftharpoons HS^-(aq)\] \[HS^-(aq) + H^+(aq) \rightleftharpoons H2S(g)\] For chloride ion (Cl⁻): \[Cl^-(aq) + H^+(aq) \rightarrow \text{No reaction}\] In acidic solutions, sulfide ions combine with H⁺ ions to form H2S gas which escapes from the solution, effectively removing sulfide ions from the solution. This reduces the concentration of S²⁻ ions, allowing more Ag2S to dissolve and establish equilibrium. On the other hand, chloride ions do not react with H⁺ ions in acidic environments, and thus their concentration is not affected.

Step 3: Compare the solubility of silver sulfide and silver chloride in acidic environments

Based on the behavior of these compounds in acidic solutions, we can conclude the following: Silver sulfide (Ag2S) is more likely to dissolve in acidic solutions when compared to silver chloride (AgCl). This is because, in acidic environments, sulfide ions combine with H⁺ ions to form H2S gas, which escapes the solution, decreasing the concentration of S²⁻ ions and allowing more Ag2S to dissolve to re-establish equilibrium. In contrast, silver chloride (AgCl) does not react with H⁺ ions, and its dissolution is not influenced by the acidity of the solution. So, the answer is: Silver sulfide (Ag2S) is more likely to dissolve in an acidic solution. The reason is that in acidic environments, sulfide ions combine with H⁺ ions to form H2S gas and decrease the concentration of S²⁻ ions, allowing more Ag2S to dissolve.