For this problem, we’re being asked to calculate the **concentration of Pb ^{2+}** needed in order to precipitate

Dissociation reaction: PbF_{2}(s) ⇌ **Pb ^{2+}(aq)** + 2F

**Step 1**: ICE Chart

**Step 2: **K_{sp} expression

$\overline{){{\mathbf{K}}}_{{\mathbf{sp}}}{\mathbf{=}}\frac{\mathbf{products}}{\overline{)\mathbf{reactants}}}{\mathbf{=}}\mathbf{\left[}{\mathbf{Pb}}^{\mathbf{2}\mathbf{+}}\mathbf{\right]}{\mathbf{\left[}{\mathbf{F}}^{\mathbf{-}}\mathbf{\right]}}^{{\mathbf{2}}}}$

*Note that each concentration is raised by the stoichiometric coefficient*

What concentration of the lead ion, Pb2+ , must be exceeded to precipitate PbF2 from a solution that is 1.00?10?2 *M* in the fluoride ion, F? ? *K*sp for lead(II) fluoride is 3.3?10^{?8} .

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