Separate samples of a solution of an unknown ionic compound are treated with dilute AgNO3, Pb1NO322, and BaCl2. Precipitates form in all three cases. Which of the following could be the anion of the unknown salt: Br-, CO32-, NO3-?

Key Concepts

Precipitation Reactions

Precipitation reactions occur when two soluble ionic compounds react in solution to form an insoluble solid, known as a precipitate. In this case, the addition of AgNO3, Pb(NO3)2, and BaCl2 to the unknown ionic compound results in precipitates, indicating that the anion in the unknown compound must form insoluble salts with these cations.

Solubility Rules

Solubility rules are guidelines that help predict whether a compound will dissolve in water. For example, silver (Ag+), lead (Pb2+), and barium (Ba2+) salts have specific solubility characteristics; AgBr and PbBr2 are insoluble, while BaCO3 is also insoluble. Understanding these rules is essential for determining which anions can form precipitates with the given cations.

Ionic Compounds and Anions

Ionic compounds consist of cations and anions held together by ionic bonds. The identity of the anion is crucial in predicting the behavior of the compound in solution. In this scenario, the possible anions Br-, CO32-, and NO3- must be evaluated based on their ability to form precipitates with the cations present in the reagents used.