A solution contains 0.50 M lead ions, P b 2 + , and 0.00010 M zinc ions, Z n 2 + . If solid N...


A solution contains 0.50 M lead ions, {eq}Pb^{2+} {/eq}, and 0.00010 M zinc ions, {eq}Zn^{2+} {/eq}. If solid {eq}Na_2S {/eq} is slowly added to the solution, which salt precipitates first, {eq}PbS {/eq} or {eq}ZnS {/eq}? What is the concentration of the first ion that precipitates when the second or more soluble salt begins to precipitate?

Selective Precipitation:

Selective precipitation uses a precipitation reaction as a method to separate some number of metal cation species present inside of a single aqueous solution. Precipitation is initiated by adding a common anion species that forms insoluble salt compounds with the cations to be separated. The insoluble compounds do not precipitate at the same added added molarity of the common anion. They precipitate sufficiently far apart due to significantly differing {eq}K_{sp} {/eq} values. Ideally, over 99% of one cation will be removed as a precipitate before the next cation begins to precipitate in the sequence.

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This question deals with selective precipitation that forms insoluble salt compound products of PbS and ZnS. The solubility equilbria of these...

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The Common Ion Effect and Selective Precipitation


Chapter 11 / Lesson 6

Learn about the common ion effect on solubility. Learn what a common ion is, examine a common ion chart, and work through examples of the common ion effect.

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