A solution contains 0.021 M Cl and 0.017 M I. A solution containing copper (I) ions is added to selectively precipitate one of the ions. At what concentration of copper (I) ion will a precipitate begin to form? What is the identity of the precipitate? Ksp(CuCl) = 1.0 × 10-6, Ksp(CuI) = 5.1 × 10-12.

Respuesta :

Answer: Copper (I) iodide will precipitate first.

Explanation:

We are given:

[tex]K_{sp}[/tex] of CuCl = [tex]1.0\times 10^{-6}[/tex]

[tex]K_{sp}[/tex] of CuI = [tex]5.1\times 10^{-12}[/tex]

Concentration of [tex]Cl^-\text{ ion}=0.021M[/tex]

Concentration of [tex]I^-\text{ ion}=0.017M[/tex]

Solubility product is defined as the product of concentration of ions present in a solution each raised to the power its stoichiometric ratio.

  • For CuCl:

[tex]K_{sp}=[Cu^+][Cl^-][/tex]

Putting values in above equation, we get:

[tex]1.0\times 10^{-6}=[Cu^+]\times 0.021[/tex]

[tex][Cu^+]=\frac{1.0\times 10^{-6}}{0.021}=4.76\times 10^{-5}M[/tex]

Concentration of copper (I) ion = [tex]4.76\times 10^{-5}M[/tex]

  • For CuI:

[tex]K_{sp}=[Cu^+][I^-][/tex]

Putting values in above equation, we get:

[tex]5.1\times 10^{-12}=[Cu^+]\times 0.017[/tex]

[tex][Cu^+]=\frac{5.1\times 10^{-12}}{0.017}=3.00\times 10^{-10}M[/tex]

Concentration of copper (I) ion = [tex]3.00\times 10^{-10}M[/tex]

For the precipitation of copper (I) ions, we need less concentration of copper (I) ions. So, copper (I) iodide will precipitate first.