Which ion is identified by forming a white precipitate with acidified barium chloride solution?

Which ion is identified by forming a white precipitate with acidified barium chloride solution?

• A. Sulfate ions
• B. Chloride ions
• C. Bromide ions
• D. Iodide ions

Answer: (A)

The key idea is that sulfate ions form an insoluble salt with barium ions. When barium chloride is added in acidic solution, sulfate ions make barium sulfate (BaSO4), which is highly insoluble and appears as a white precipitate. The acid removes interference from other species like carbonates, so they won’t precipitate BaCO3. Halide ions such as chloride, bromide, and iodide don’t form insoluble barium salts under these conditions, so no precipitate appears. That distinctive white solid identifies sulfate ions.

The key idea is that sulfate ions form an insoluble salt with barium ions. When barium chloride is added in acidic solution, sulfate ions make barium sulfate (BaSO4), which is highly insoluble and appears as a white precipitate. The acid removes interference from other species like carbonates, so they won’t precipitate BaCO3. Halide ions such as chloride, bromide, and iodide don’t form insoluble barium salts under these conditions, so no precipitate appears. That distinctive white solid identifies sulfate ions.