We can cause a sparingly soluble salt to precipitate out of solution if the product of the concentration of the ions concerned exceeds the Ksp.
Say I have 50.0cm3 of 0.050 mol dm-3 silver nitrate and 50.0cm3 of 0.010 mol dm-3 potassium bromate, and I pour one solution into the other. Given that the solubility product of silver bromate is 6.0 x 10-5 mol2 dm-6, will the solid precipitate out?
- Determine the [Ag+(aq)] and the [BrO3–(aq)] in the mixed solution.
- Work out the total ion concentration in the mixture and compare against the Ksp.
Practice questions
Show by calculation whether a precipitate will form when 30cm3 of each of the following solutions are mixed:
(a) 1.0 x 10-3 mol dm-3 of silver nitrate and 1.0 x 10-3 mol dm-3 sodium chloride
(b) 1.3 x 10-3 mol dm-3 of lead(II) nitrate and 1.0 x 10-3 mol dm-3 potassium bromide
| Salt | Solubility product |
| AgCl | 2.0 x 10-10 mol2 dm-6 |
| PbBr2 | 3.9 x 10-5 mol3 dm-9 |
Answers
