Question

In this lab, biology students were directed to use indicators as chemical detection tools, to analyze a variety of foods for the presence of carbohydrates, lipids or proteins. One group of students was given four unmarked containers of sugars: glucose, sucrose, fructose, and galactose. How could they use the standard lab tests to find the sucrose? A) They could use the Benedict's test; sucrose would have a positive Benedict's test and the other sugars would not. B) They could use the Biuret test; it would not have a positive reaction for sucrose but it would for the other three sugars. C) They could use the Benedict's test; it would not have a positive reaction for sucrose but it would for the other three sugars. D) They could use the iodine test; because sucrose is not a monosaccharide, it would have a positive iodine test and the others would not.

Answer 1

The Answer is B: They could use the Benedict's test; it would not have a positive reaction for sucrose but it would for the other three sugars.

Answer 2

The correct answer is option C) They could use the Benedict's test; it would not have a positive reaction for sucrose but it would for the other three sugars.

The Benedict's test can detect the free aldehyde or the ketonic group present in the molecule. All the monosaccharides gives a positive Benedict's test. The fructose, glucose and galactose all the monosaccharides and gives a positive Benedict's test, but the sucrose is a disaccharides and it does not give a positive Benedict's Test. Hence, it can be used to identify Sucrose.