91Ó°ÊÓ

State in words the meaning of the solubility product equation for \(\mathrm{PbI}_{2}\) : $$ K_{\mathrm{xp}}=\left[\mathrm{Pb}^{2+}\right]\left[\mathrm{I}^{-}\right]^{2} $$

When \(5.0 \mathrm{mL}\) of \(0.012 \mathrm{M} \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}\) are mixed with \(5.0 \mathrm{mL}\) of \(0.030 \mathrm{M} \mathrm{KI},\) a yellow precipitate of \(\mathrm{PbI}_{2}(\mathrm{s})\) forms. a. How many moles of \(\mathrm{Pb}^{2+}\) are initially present?\(\quad\quad\) __________ moles b. How many moles of \(I^{-}\) are originally present?\(\quad\quad\) __________ moles c. In a colorimeter the cquilibrium solution is analyzed for \(\mathrm{I}^{-}\), and its concentration is found to be \(7 \times\) \(10^{-3}\) mole/liter. How many moles of \(\mathbf{I}^{-}\) are present in the solution ( \(10 \mathrm{ml}\) )? __________ moles d. How many moles of I - precipitated?\(\quad\quad\) __________ moles e. How many moles of \(\mathrm{Pb}^{2+}\) precipitated?\(\quad\quad\) __________ moles f. How many moles of \(\mathrm{Pb}^{2+}\) are left in solution?\(\quad\quad\) __________ moles g. What is the concentration of \(\mathrm{Pb}^{2+}\) in the equilibrium solution?\(\quad\quad\) __________ moles/liter h. Find a value for \(K_{\mathrm{sp}}\) of \(\mathrm{PbI}_{2}\) from these data.\(\quad\quad\) __________

In another experiment a small sample of pure \(\mathrm{PbI}_{2}\) is shaken with water to produce a saturated solution, a. What must be the relationship between \(\left[\mathrm{Pb}^{2+}\right]\) and \(\left[\mathrm{I}^{-}\right]\) in that solution? (See Reaction 1.) b. The concentration of \(\mathrm{I}\) - in the saturated solution is found to be \(5.0 \times 10^{-3} \mathrm{M}\). What is the concentration of \(\mathrm{Pb}^{2+}\) ion? __________ M c. Using the results of Part b, calculate a value for \(K_{\mathrm{sp}}\) for \(\mathrm{PbI}_{2}\). (Use Eq. 1.) __________