Silver chloride is a sparingly soluble salt.
AgCl(s) ⇌ Ag+(aq) + Cl–(aq)
Ksp = [Ag+(aq)] [Cl–(aq)] = 2.0 x 10-10 mol2 dm-6
If I try to dissolve silver chloride in a solution of sodium chloride rather than water (just go with me here), will it be more or less soluble? The chloride ion represents the common ion in this example and we can either use le Chatelier’s principle to answer this question qualitatively or we can calculate an answer.
According to le Chatelier, addition of NaCl will increase the chloride ion concentration so the position of equilibrium will shift to the left. More AgCl(s) will precipitate out. Adding chloride ions effectively reduces the silver ion concentration and the solubility of silver chloride.
Let’s put some numbers to this …
Calculate the solubility of silver chloride in (a) pure water and (b) 0.15 mol dm-3 NaCl(aq).
Silver chloride is 10,000 times less soluble in NaCl than it is in pure water – the common ion effect is significant!
Practice questions
Calculate the solubility of strontium sulphate, SrSO4, in 0.1 mol dm-3 sodium sulphate, given that its solubility product is 4.0 x 10-7 mol2 dm-6.
Answer
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