Question

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. benedict reagent was not added to tube c.
b. tube c was not heated for the correct amount of time.
c. tube c was contaminated by the contents of one of the other tubes.
d. the solution added to tube c did not contain simple sugar.

Explanation:

Analyze the observed color in Tube C

Tube C remains blue, which is the color of unreacted Benedict's reagent, indicating a negative test result (no reducing sugar detected).

Evaluate the potential explanations for a negative result

• A. Benedict reagent was not added to Tube C: Incorrect, because the solution is bright blue, which is the characteristic color of Benedict's reagent itself.
• B. Tube C was not heated for the correct amount of time: Correct, because Benedict's test requires heat to initiate the reduction reaction; without sufficient heating, even a solution containing glucose will remain blue.
• C. Tube C was contaminated by the contents of one of the other tubes: Incorrect, because the other tubes (A, B, D) contain reducing sugars (green, red, orange-brown results). Contamination with these would yield a positive (non-blue) result.
• D. The solution added to Tube C did not contain simple sugar: Correct, because a solution lacking reducing sugars (like glucose) will not react with the reagent, leaving it blue.

Answer:

• A. Benedict reagent was not added to Tube C.
• B. Tube C was not heated for the correct amount of time. (Correct answer)
• C. Tube C was contaminated by the contents of one of the other tubes.
• D. The solution added to Tube C did not contain simple sugar. (Correct answer)