A mineral sample is analyzed for its cobalt and calcium content. A sample is dissolved, and then the cobalt and calcium are precipitated as Co(OH)2(s) and Ca(OH)2(s). At what pH can Co(OH)2(s) be separated from Ca(OH)2(s) at 25 °C? Assume that an effective separation requires a maximum concentration of the less soluble hydroxide of 1× 10^–6 M.

Question

A mineral sample is analyzed for its cobalt and calcium content. A sample is dissolved, and then the cobalt and calcium are precipitated as Co(OH)2(s) and Ca(OH)2(s). At what pH can Co(OH)2(s) be separated from Ca(OH)2(s) at 25 °C? Assume that an effective separation requires a maximum concentration of the less soluble hydroxide of 1× 10^–6 M.  
Ksp[Co(OH02]=5.9e-15
Ksp[Ca(OH02]=5.0e-6
What is the concentration of the more soluble hydroxide at this pH?

I got 9.89 for the pH, and that was right. I am having trouble with the concentration.

Anonymous · Answer

kj 457/854=78mol 22*';p