45. What reagent might be used to separate the ions in each...

45. What reagent might be used to separate the ions in each of the following mixtures, which are 0.1$M$ with respect to each ion? In some cases it may be necessary to control the pH. (Hint: Consider the $K_{\text { sp values given in }}$Appendix J.) (a) $\mathrm{Hg}_{2}^{2+}$ and $\mathrm{Cu}^{2+}$ (b) $\mathrm{SO}_{4}^{2-}$ and $\mathrm{Cl}^{-}$ (c) $\mathrm{Hg}^{2+}$ and $\mathrm{Co}^{2+}$ (d) $\mathrm{Zn}^{2+}$ and $\mathrm{Sr}^{2+}$ (e) $\mathrm{Ba}^{2+}$ and $\mathrm{Mg}^{2+}$ (f) $\mathrm{CO}_{3}^{2-}$ and $\mathrm{OH}^{-}$

45. What reagent might be used to separate the ions in each of the following mixtures, which are 0.1$M$ with respect to each ion? In some cases it may be necessary to control the pH. (Hint: Consider the $K_{\text { sp values given in }}$Appendix J.)
(a) $\mathrm{Hg}_{2}^{2+}$ and $\mathrm{Cu}^{2+}$
(b) $\mathrm{SO}_{4}^{2-}$ and $\mathrm{Cl}^{-}$
(c) $\mathrm{Hg}^{2+}$ and $\mathrm{Co}^{2+}$
(d) $\mathrm{Zn}^{2+}$ and $\mathrm{Sr}^{2+}$
(e) $\mathrm{Ba}^{2+}$ and $\mathrm{Mg}^{2+}$
(f) $\mathrm{CO}_{3}^{2-}$ and $\mathrm{OH}^{-}$

Key Concepts

Precipitation Reactions

Precipitation reactions occur when ions in solution combine with added reagents to form an insoluble compound, which separates out as a solid. This process is governed by the conditions of the reaction and the solubility product constant, and it is widely used to separate and identify ionic species.

Solubility Product (Ksp)

The solubility product, denoted as Ksp, is the equilibrium constant for the dissolution of a sparingly soluble salt. It quantifies the maximum concentrations of the constituent ions that can exist in solution before the salt begins to precipitate, allowing chemists to predict and control precipitation reactions.

Selective Precipitation

Selective precipitation is the process of adding a reagent that precipitates a specific ion from a mixture, based on differences in solubility or Ksp values of the resulting compounds. This technique enables the separation of ions that might otherwise remain in solution together.

pH Control in Precipitation Reactions

The pH of a solution can affect the solubility of various compounds by influencing the ionization state of the involved species. Controlling the pH is crucial in precipitation reactions because it can be used to favor the formation of one precipitate over another, enhancing selectivity in ion separation.

Reagent Selection

Reagent selection involves choosing an appropriate chemical that reacts with one or more ions to form a precipitate, based on solubility considerations and the reaction conditions. This process is essential for designing separation strategies in analytical and preparative chemistry, ensuring that only the desired ions are removed from the solution.

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