Final answer:
The pair of aqueous solutions that will form a precipitate when mixed is not found between NH4Cl and NaBr or CaCl₂ and CsI, as the ions involved in these mixtures are all soluble in water.
Step-by-step explanation:
The student's question asks which pair of aqueous solutions, when mixed, will form a precipitate. To answer which pairs will react to form a precipitate, we can use solubility rules and look at the possible combinations of ions that would produce an insoluble compound. For example, when CaCl₂ is mixed with CsI, there is no formation of a precipitate since all the possible combinations of ions (Ca²⁺, Cl⁻, Cs⁺, and I⁻) remain soluble in water.
From the provided examples, we can infer that certain cation and anion pairs are known to form precipitates, such as Pb²⁺ with SO₄²⁺, Ba²⁺ with SO₄²⁺, and Ag⁺ with Cl⁻. In this context, the answer to the original question is option (d) CaCl₂ (Calcium Chloride) and CsI (Cesium Iodide) will not form a precipitate when mixed.
To determine which pair of aqueous solutions will form a precipitate when mixed, we need to consult the solubility rules. According to the solubility rules, compounds like NH4Cl and NaBr are soluble in water, so they will not form a precipitate when mixed. On the other hand, CaCl₂ and CsI will form a precipitate when mixed because it contains ions (Ca²⁺ and I⁻) that are not soluble with each other.