If a solution containing 0.015 M each of bromide, chloride, iodide, and thiocyanate, is treated with Cu+, in what order will the anions precipitate?
Take CuBr as an example: The Ksp value is 6.3E-9 but make sure you use the Ksp values in your notes or your text.
................CuBr ===> Cu^+ + Br^-
I................solid...........0...........0
C..............solid............x............x
E..............solid.............x............x
Ksp = 6.3E-9 = (Cu^+)(Br^-)
(Cu^+) = x
(Br^-) = 0.15 M from the problem.
Substitute
6.3E-9 = (x)(0.15)..
Then x = (Cu^+) = 6.3E-9/0.15 = ?
Do the same for all of the salts. The one with the smallest value for Cu will ppt first followed in order by the others. Post your work if you get stuck.
Thank you so much for your help.
To determine the order in which the anions will precipitate when treated with Cu+, we need to compare the solubility product constants (Ksp) of the various copper salts formed with bromide (Br-), chloride (Cl-), iodide (I-), and thiocyanate (SCN-).
The solubility product constant (Ksp) is a measure of the solubility of a compound. It indicates the concentration of ions at which a solid compound will start to precipitate.
Here are the solubility product constants for the copper salts with the ions mentioned:
- Copper bromide (CuBr): Ksp = 6.3 × 10^-9
- Copper chloride (CuCl): Ksp = 1.1 × 10^-7
- Copper iodide (CuI): Ksp = 6.3 × 10^-12
- Copper thiocyanate (CuSCN): Ksp = 2.0 × 10^-4
The anions will precipitate in order of increasing Ksp values, meaning the anion with the lowest Ksp will precipitate first, followed by the higher Ksp values.
Comparing the Ksp values, we can determine that the order in which the anions will precipitate is as follows:
1. Copper iodide (CuI) will precipitate first since it has the lowest Ksp value.
2. Copper bromide (CuBr) will precipitate next since it has a higher Ksp value than CuI but lower than the remaining anions.
3. Copper chloride (CuCl) will precipitate afterward since it has a higher Ksp value than CuBr but lower than CuSCN.
4. Copper thiocyanate (CuSCN) will precipitate last since it has the highest Ksp value among the mentioned anions.
So, the order in which the anions will precipitate when treated with Cu+ is: Iodide (I-) > Bromide (Br-) > Chloride (Cl-) > Thiocyanate (SCN-).