Assignment:
Solubility of a Salt & “Salting In”
The solubility product of the sparingly-soluble salt Ag2S in water, ksp = 6 x 10-51 at 25 °C, represents the reaction:
2 Ag(s) + S(rh) ↔ Ag2S(aq)
where silver sulfide dissociates completely into silver and sulfide ions upon dissolution in water. Here S(rh) stands for rhombic crystalline solid sulfur, the reference form of this element and its most stable form at 1 bar and 298.15 K.
a. What is the molal solubility of Ag2S, bag2s (in mol/kg), in pure water at 25 °C?
b. Experimentally we observe that the presence of a second very soluble salt increases the solubility of a sparingly-soluble species, a phenomenon known as “salting in” and used to increase the solubility of proteins. What is the molal solubility (in mol/kg) of Ag2S in an aqueous solution of 5 x 10 -2 mol/kg NaCl(aq)? Assume that the ionic strength is dominated by the contributions from NaCl.
Provide complete and step by step solution for the question and show calculations and use formulas.