Lugol's solution consists of what?

Lugol's solution consists of what?

• A. 2% I2 in NaI + water
• B. 5% I2 in NaI + water
• C. 5% I2 in KI + water
• D. 7.5% I2 in KI + alcohol

Answer: (C)

Iodine doesn’t dissolve well in water on its own, but when iodide ions are present, iodine forms a soluble I3– complex. Lugol’s solution uses potassium iodide to provide those iodide ions, allowing iodine to stay dissolved in water. That’s why the description of 5% I2 in KI dissolved in water best matches Lugol’s solution, which is typically about 5% iodine with 10% potassium iodide in water. The other options differ by the iodide source, solvent, or iodine concentration, so they don’t describe Lugol’s solution correctly.

Iodine doesn’t dissolve well in water on its own, but when iodide ions are present, iodine forms a soluble I3– complex. Lugol’s solution uses potassium iodide to provide those iodide ions, allowing iodine to stay dissolved in water. That’s why the description of 5% I2 in KI dissolved in water best matches Lugol’s solution, which is typically about 5% iodine with 10% potassium iodide in water. The other options differ by the iodide source, solvent, or iodine concentration, so they don’t describe Lugol’s solution correctly.