A student is performing a Benedict’s test on an unknown substance. The student adds the reagent (the chemical required to make a color change), and nothing happens. Which conclusion can the student make?

Question

The test was inconclusive because the student needed to also test with iodine or vinegar.
The test was inconclusive because the student needed to also test with iodine or vinegar.
The substance is not glucose based.
The substance is glucose based.
The test was inconclusive because the student forgot to add heat.

Answer 1

In the Benedict’s test, a color change occurs when reducing sugars, such as glucose, are present. If the student added the Benedict’s reagent and observed no color change, the student can conclude that the substance likely does not contain reducing sugars, such as glucose.

While the statement "The test was inconclusive because the student forgot to add heat" could also be a valid consideration (since the Benedict's test typically requires heating to see a color change), the primary conclusion that can be drawn based on the lack of color change is that:

The substance is not glucose based.

This conclusion assumes the test was conducted correctly (including heating) and that the temperature of the reaction was appropriate. If there was indeed a mistake (like forgetting to heat), the conclusion about the substance's sugar content could be reevaluated later.