In the Ferric Reduction method, what are the colors of the reagents before and after reaction with glucose?

• A. Yellow-orange (reagent) and colorless (product)
• B. Blue (reagent) and green (product)
• C. Red (reagent) and colorless (product)
• D. Colorless (reagent) and yellow-orange (product)

Answer: (A)

In the Ferric Reduction Method, reducing sugars like glucose donate electrons to ferric ions (Fe3+), converting them to ferrous ions (Fe2+). The ferric complex in the reagent has a yellow-orange color, so the solution appears yellow-orange before the reaction. When glucose reduces Fe3+ to Fe2+, the colored ferric form is removed and the product is colorless, so the solution decolorizes. Thus the reagent is yellow-orange initially and becomes colorless after reacting with glucose.