Barium sulfate is ...

Barium sulfate is ...

• A. Soluble
• B. Insoluble
• C. Partly soluble
• D. Dissolves in water

Answer: (B)

Solubility of ionic compounds in water is being tested here. Barium sulfate has exceptionally low solubility in water, so only a tiny amount dissolves to form Ba2+ and SO4^2− ions. The dissolution equilibrium is so unfavourable that the solubility product is very small (about 1 × 10^−10), which means the vast majority stays as solid BaSO4 rather than going into solution. So it is classified as insoluble in water. This very low solubility explains why it’s used as a contrast agent in medical imaging—the solid remains in place rather than releasing ions into the body. Saying it dissolves in water or is partly soluble would imply a significant amount of ions form in solution, which doesn’t happen with BaSO4.

Solubility of ionic compounds in water is being tested here. Barium sulfate has exceptionally low solubility in water, so only a tiny amount dissolves to form Ba2+ and SO4^2− ions. The dissolution equilibrium is so unfavourable that the solubility product is very small (about 1 × 10^−10), which means the vast majority stays as solid BaSO4 rather than going into solution. So it is classified as insoluble in water. This very low solubility explains why it’s used as a contrast agent in medical imaging—the solid remains in place rather than releasing ions into the body. Saying it dissolves in water or is partly soluble would imply a significant amount of ions form in solution, which doesn’t happen with BaSO4.