Final answer:
Option D, calcium chloride and potassium phosphate, is the combination that would not form a precipitate in an aqueous solution, as all potential products are soluble in water under typical laboratory conditions.
Step-by-step explanation:
To determine which of the given combinations would not form a precipitate in an aqueous solution, we must consider the solubility rules. A precipitation reaction occurs in a double-replacement reaction when the new combinations of ions form an insoluble compound.
- A. Sodium chloride and silver nitrate: This combination will form a precipitate of silver chloride (AgCl), which is insoluble in water.
- B. Barium chloride and sodium sulfate: This combination will form a precipitate of barium sulfate (BaSO4), which is insoluble in water.
- C. Potassium iodide and lead nitrate: This combination will form a precipitate of lead iodide (PbI2), which is insoluble in water.
- D. Calcium chloride and potassium phosphate: Here, all potential products are soluble in water. Calcium phosphate is moderately soluble, but with typical concentrations found in a laboratory, it may not precipitate. Therefore, this combination is less likely to form a precipitate compared to the others listed.
Based on this information, the correct answer is D. calcium chloride and potassium phosphate, as it is the combination least likely to form a precipitate under typical conditions.