Question

if a test tube contained a clear solution of starch, what would you predict would be the result of a benedicts test on this sample? the reagent test results in a test tube that is red, indicating a positive result. the reagent test results in a test tube that is blue, indicating a negative result. the reagent test results in a test tube that is red indicating a negative result. the reagent test results in a test tube that is clear, indicating a negative result. the reagent test results in a test tube that is blue, indicating a positive result. 2.5 pts question 2 if a well on a spot plate contained a clear solution of glucose (monomers), what would you predict would be the result of an iodine test on this sample? the reagent test results in a well that is yellow - brown, indicating a positive result. the reagent test results in a well that is yellow - brown indicating a negative result. the reagent test results in a well that is clear, indicating a negative result. the reagent test results in a well that is blue - black, indicating a negative result. the reagent test results in a well that is blue - black, indicating a positive result.

Explanation:

1. Benedict's test is used to detect reducing sugars. Starch is a polysaccharide and not a reducing sugar, so a negative result (blue color due to the copper - sulfate in Benedict's reagent remaining unreacted) is expected.
2. Iodine test is used to detect starch. Glucose is a monosaccharide and not starch. So, a negative result (yellow - brown color of iodine solution remaining unreacted) is expected.

Answer:

1. The reagent test results in a test tube that is blue, indicating a negative result.
2. The reagent test results in a well that is yellow - brown, indicating a negative result.