Which statement about Benedict's reagent and reducing sugars is true?

Which statement about Benedict's reagent and reducing sugars is true?

• A. It measures a sugar's reducing ability to donate electrons.
• B. It measures the salt content of a solution.
• C. It detects lipids in a solution.
• D. It indicates the pH level of a solution.

Answer: (D)

Benedict's reagent tests for reducing sugars by their ability to donate electrons to copper(II) ions in the alkaline solution. When a reducing sugar is present, it is oxidized (its aldehyde or enediol form can be reduced), and Cu2+ is reduced to Cu+, producing a color change from blue toward green, yellow, orange, and brick red as the amount of reducing sugar increases. A precipitate of copper(I) oxide often forms as the reaction proceeds. This test specifically measures reducing capability, not pH, salt content, or lipids, which are detected by other methods. Note that non-reducing sugars won’t give a positive result unless they are first hydrolyzed to give reducing monosaccharides.

Benedict's reagent tests for reducing sugars by their ability to donate electrons to copper(II) ions in the alkaline solution. When a reducing sugar is present, it is oxidized (its aldehyde or enediol form can be reduced), and Cu2+ is reduced to Cu+, producing a color change from blue toward green, yellow, orange, and brick red as the amount of reducing sugar increases. A precipitate of copper(I) oxide often forms as the reaction proceeds. This test specifically measures reducing capability, not pH, salt content, or lipids, which are detected by other methods. Note that non-reducing sugars won’t give a positive result unless they are first hydrolyzed to give reducing monosaccharides.