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A metal plating solution contains 50.00 mg/L of copper. Determine the concentration, in moles/L, to which the hydroxide concentration must be raised to precipitate all but 1.3 mg/L of the copper using lime. The Ksp of copper hydroxide is 2.00 3 10219. Estimate the final pH (report your answer to two decimal places).

Respuesta :

Answer:

[tex]pH=6.51[/tex]

Explanation:

Given:

  • The concentration of Cu initially = [tex]50mgL^{-1} = \frac{50*10^{-3}}{63.5}=0.787*10^{-3}molL^{-1}[/tex]
  • The concentration of Cu finally = [tex]1.3mgL^{-1} = \frac{1.3*10^{-3}}{63.5}=0.0205*10^{-3}molL^{-1}[/tex]
  • [tex]K_{sp}=2.20*10^{-20}[/tex] -This is the actual [tex]K_{sp}[/tex] of [tex]Cu(OH)_2[/tex]

We know that ,

[tex]Cu(OH)_2[/tex]⇒[tex]Cu^{2+}+2OH^-[/tex]

Therefore ,

[tex]K_{sp}=[Cu^{2+}][OH^-]^2[/tex]

[tex]2.20*10^{-20}=0.0205*10^{-3}*[OH^-]^2\\1.0731*10^{-15}=[OH^-]^2\\3.276*10^{-8}=[OH^-][/tex]

[tex]pOH=-log[OH^-]\\\\pOH=-log(3.276*10^{-8})\\pOH=7.485\\pH=14-pOH\\pH=14-7.49\\pH=6.51[/tex]

Answer: [tex]pH=6.51[/tex]