Questions: Michael has tested 4 different solutions of variable glucose concentration with Benedict reagent. What are the possible explanations for the result observed in Tube C? Select all that apply A. The solution added to Tube C did not contain simple sugar. B. Tube C was not heated for the correct amount of time. C. Benedict reagent was not added to Tube C. D. Tube C was contaminated by the contents of one of the other tubes.

Solution Steps

Benedict's test is used to detect the presence of reducing sugars, like glucose. A positive test result is indicated by a color change, ranging from green (low concentration) to yellow/orange/red/brown (high concentration). A blue color indicates a negative test, meaning a very low or no concentration of reducing sugars. Tube C shows a blue color, indicating a negative result.

• A. The solution added to Tube C did not contain simple sugar. This is a valid explanation. If there's no glucose (or another reducing sugar), the test will be negative and remain blue.

• B. Tube C was not heated for the correct amount of time. Benedict's test requires heat. Insufficient heating can prevent the reaction from occurring and produce a false negative (blue color). This is a plausible explanation.

• C. Benedict reagent was not added to Tube C. If the reagent wasn't added, the reaction wouldn't occur, and the solution would likely remain the original color of the tested solution which could be blue, leading to a false negative. This is a valid explanation.

• D. Tube C was contaminated by the contents of one of the other tubes. Contamination from another tube would likely introduce glucose into Tube C, resulting in a color change. This would not explain the blue color.

Options A, B, and C provide valid explanations for the blue color in Tube C.

Final Answer