Question

Benedict reagent test is conducted to confirm the presence of
A. Protein
B. Lipid
C. Starch
D. Reducing sugar

Answer 1

Hint: Benedict reagent is a chemical reagent containing a complex mixture of sodium carbonate, sodium citrate, and copper(II) sulfate pentahydrate. It is most commonly used in place of Fehling’s solution. The tests in which Benedict reagent is used are called the Benedict reagent test.

Complete answer: Reducing sugars are any sugars that contain free aldehyde groups or free ketone groups due to which it acts as a reducing agent (a compound that loses an electron to an oxidizing agent). All monosaccharides are reducing sugars. Benedict reagent is a chemical reagent containing a complex mixture of sodium carbonate, sodium citrate, and copper(II) sulfate pentahydrate. It is used in place of Fehling’s solution to detect reducing sugars if present. The tests which use this reagent are called the Benedict reagent test. Reducing sugars gives a positive result to this test.
When the test is positive, the Benedict reagent shows a change in colour from clear blue to brick red along with a precipitate. They detect the presence of aldehyde, ketones, and hemiacetals.
The test is performed as follows: a substance containing reducing sugar is mixed with water then Benedict reagent is added. The solution is boiled for a few minutes and then is cooled. The appearance of red, yellow, or green colour confirms the presence of reducing sugars.
Therefore, the correct answer is option D.

Note: Benedict reagent is a mixture of chemicals that is used to perform the test for the presence of reducing sugars (aldehyde, ketones, hemiacetals). The substance having reducing sugars is mixed with the reagent and is boiled for a few minutes. The change of colour to red shows a positive result.