Chapter 16, Problem 87AE

Calculate the concentration of Pb²⁺ in each of the following.

a. a saturated solution of Pb(OH)₂, K_sp = 1.2 × 10⁻¹⁵

b. a saturated solution of Pb(OH)₂ buffered at pH = 13.00

c. Ethylenediaminetetraacetate (EDTA⁴⁻) is used as a complexing agent in chemical analysis and has the following structure:

Solutions of EDTA⁴⁻ are used to treat heavy metal poisoning by removing the heavy metal in the form of a soluble complex ion. The reaction of EDTA⁴⁻ with Pb²⁺ is

$\begin{array}{cc}{\text{Pb}}^{2+}(aq)+EDT{A}^{4-}(aq)\rightleftharpoons PbEDT{A}^{2-}(aq)& K=1.1\times {10}^{18}\end{array}$

Consider a solution with 0.010 mole of Pb(NO₃)₂ added to 1.0 L of an aqueous solution buffered at pH = 13.00 and containing 0.050 M Na₄.EDTA. Does Pb(OH)₂ precipitate from this solution?