Describe how you could separate the ions in each of the...

Describe how you could separate the ions in each of the following groups by selective precipitation.
a. $\mathrm{Ag}^{+}, \mathrm{Mg}^{2+}, \mathrm{Cu}^{2+}$
c. $\mathrm{Pb}^{2+}, \mathrm{Bi}^{3+}$
b. $\mathrm{Pb}^{2+}, \mathrm{Ca}^{2+}, \mathrm{Fe}^{2+}$

Key Concepts

Selective Precipitation

Selective precipitation is a separation technique that relies on the different solubilities of a set of ions when exposed to a precipitating agent. By carefully choosing the reagent and controlling the concentration, one can precipitate one ion as an insoluble salt while keeping others in solution, thereby achieving separation based on differences in solubility.

Solubility Product Constant (Ksp)

The solubility product constant, Ksp, represents the equilibrium constant for the dissolution of an ionic compound in water. It is a measure of how much of the compound can dissolve before the solution becomes supersaturated. In selective precipitation, differences in the Ksp values of potential precipitates determine the order in which ions will precipitate out of the solution.

Precipitation Reactions

Precipitation reactions occur when ions in solution combine to form an insoluble compound, resulting in the formation of a solid precipitate. Understanding the chemical reactions that lead to the formation of these precipitates is crucial in designing a stepwise separation process, where the precipitate’s selectivity is governed by its low solubility in the aqueous medium.

Common Ion Effect

The common ion effect refers to the phenomenon where the solubility of an ionic compound is reduced due to the presence of a common ion already in the solution. This effect can be used to further control the precipitation process by manipulating ion concentrations, ensuring that only the desired ion precipitates under the given conditions.

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