Benedicts tests for reducing sugars

Question 1

Steps for the benedicts test for reducing sugars (Qualitative)

Answer 1

1. Small amount of sample placed in test tube with the same volume of benedicts solution.
2. Heat this in a water baths at 95’C.
3. Brick red/ Orange = Positive
4. Blue = No reducing sugar

Question 2

When is the semi-qualitative benedicts test useful

Answer 2

When comparing concentrations of reducing sugars

Question 3

What are the control variables that must be standardised when doing the semi-qualitative benedicts

Answer 3

1) Same volume of benedicts solution
2) Same volume of sample solutions
3) Heat sample for the same length of time
4) Heat sample at the same temperature

Question 4

What would the results of a semi-qualitative benedicts test look like

Answer 4

The more the reducing sugar, the stronger the colour change.
- Intense brick red = higher conc of reducing sugar
- Green/yellow = low conc of reducing sugar

Question 5

Problems that might occur with a semi-qualitative benedicts test

Answer 5

The colour is subjective

Question 6

When is the Quantitative benedicts test used

Answer 6

• To obtain numerical values
• To find the concentration of unknown samples

Question 6

What are the control variables that must be standardised during the quantittive

Answer 6

• Same volume of benedicts solution
• Same volume of sugar solution
• Heat for the same length of time
• Heat at the same temperature

Question 7

Steps to Quantitative benedicts test

Answer 7

1) Perform benedicts reducing sugars test on known concentrations
2) Use colorimeter to measure absorbence of each solution
3) Plot a graph. Draw a calibration curve and draw a line of best fit