A white precipitate forms with barium chloride. This indicates the presence of which ion?

A white precipitate forms with barium chloride. This indicates the presence of which ion?

• A. Sulfate (SO4 2-)
• B. Chloride (Cl-)
• C. Nitrate (NO3-)
• D. Carbonate (CO3 2-)

Answer: (A)

When barium ions are added from barium chloride to an aqueous solution, a white solid forms only if sulfate ions are present. This happens because barium sulfate (BaSO4) is extremely insoluble in water, so Ba2+ and SO4 2− combine to make a solid. Chloride and nitrate ions don’t give insoluble salts with barium, so no precipitate appears with those. Carbonate could also form BaCO3, another insoluble salt, but in standard tests the BaCl2 reaction is used as a specific indicator for sulfate because BaSO4 is very reliably insoluble and gives a persistent white precipitate.

When barium ions are added from barium chloride to an aqueous solution, a white solid forms only if sulfate ions are present. This happens because barium sulfate (BaSO4) is extremely insoluble in water, so Ba2+ and SO4 2− combine to make a solid. Chloride and nitrate ions don’t give insoluble salts with barium, so no precipitate appears with those. Carbonate could also form BaCO3, another insoluble salt, but in standard tests the BaCl2 reaction is used as a specific indicator for sulfate because BaSO4 is very reliably insoluble and gives a persistent white precipitate.