Assume that an aqueous solution of a cation, represented as a blue sphere, is allowed to mix with a solution of an anion, repre-sented as a red sphere, and that the following result is obtained: Which combinations of cation and anion, chosen from the fol-lowing lists, are compatible with the observed results? Explain Cations: Na+, Ca2+, Ag+, Ni2+ Anions: Cl-, CO3 2-, CrO4 2-, NO3

Key Concepts

Ionic Compounds and Solubility

Ionic compounds are formed from the electrostatic attraction between cations and anions. The solubility of these compounds in water depends on the nature of the ions involved. Some combinations of cations and anions will form soluble compounds, while others may precipitate out of solution. Understanding solubility rules helps predict which combinations will remain in solution.

Charge Balance in Ionic Compounds

In ionic compounds, the total positive charge from cations must balance the total negative charge from anions. This charge neutrality is essential for the stability of the compound. For example, a divalent cation like Ca2+ requires two monovalent anions like Cl- to achieve charge balance, while a monovalent cation like Na+ can pair with one Cl-.

Common Ion Effect and Precipitation

The common ion effect refers to the decrease in solubility of an ionic compound when a common ion is added to the solution. This can lead to precipitation, where the solid form of the compound separates from the solution. Identifying whether the mixing of specific cations and anions leads to precipitation is crucial for determining compatibility in the observed results.