Suggest how the cations in each of the following solution mixtures can be separated: (c) Pb2 + and Al3 +.

Verified step by step guidance

1. Identify the chemical properties of Pb^{2+} and Al^{3+} ions. Pb^{2+} is a heavy metal cation, while Al^{3+} is a lighter metal cation.
2. Consider the solubility rules for common anions. Pb^{2+} forms an insoluble precipitate with sulfate ions (SO_4^{2-}), while Al^{3+} does not.
3. Add a source of sulfate ions, such as sodium sulfate (Na_2SO_4), to the solution. This will cause Pb^{2+} to precipitate as lead sulfate (PbSO_4), which is insoluble in water.
4. Filter the mixture to separate the solid PbSO_4 from the solution. The Al^{3+} ions will remain in the aqueous phase.
5. Confirm the separation by testing the filtrate for the presence of Al^{3+} ions, which can be done by adding a reagent like sodium hydroxide (NaOH) to form aluminum hydroxide (Al(OH)_3), a gelatinous precipitate.

Key Concepts

Cation Separation Techniques

Cation separation techniques involve methods used to isolate specific cations from a mixture. Common techniques include precipitation, where a reagent is added to form an insoluble compound with one of the cations, and selective ion exchange, which utilizes resins that preferentially bind certain ions. Understanding these methods is crucial for effectively separating cations like Pb2+ and Al3+.

Solubility Product Constant (Ksp)

The solubility product constant (Ksp) is a numerical value that represents the solubility of a sparingly soluble ionic compound in water. It is essential for predicting whether a precipitate will form when two solutions are mixed. For separating Pb2+ and Al3+, knowing the Ksp values of their respective salts can guide the choice of reagents to selectively precipitate one cation over the other.

Complex Ion Formation

Complex ion formation occurs when metal cations bond with ligands to form a larger, charged species. This concept is important in cation separation because certain ligands can selectively bind to specific cations, altering their solubility and allowing for separation. For instance, adding a ligand that forms a stable complex with Pb2+ can help isolate it from Al3+ in a solution.