Lab 4: Determination of the content of reducing sugar using Benedict’s test
[Tested sample : Lucozade (glucose content : 22.48 %]

Area B1 (max. 15 marks)
Aim: ( max. 1½ )
- By use of Benedict’s test to estimate the concentration of reducing sugars
- in the given sample, Lucozade
- in term of glucose equivalent
- by comparing its reducing power with the standard glucose solution (2%)

Principle: (max. 6)
(Experimental design and principles)
Benedict’s test
- condition / test boiling of Benedict’s solution with reducing sugars / test with Benedict’s solution will give brick red precipitate

- mechanism due to presence of blue solution Cu 2+ in Benedict’s solution changed into insoluble brick-red precipitate (Cu+)

- observation and indicator for estimation
 making the resulted mixture have a gradual change of colour with amount of reducing sugars inside the solution : from blue to green, then yellow and finally brick red
 the colour of boiled mixture / the amount of precipitate at bottom of test tube as indicator of comparing concentration of reducing sugars.
 the more the ppt.  more reducing sugar

- Expected result similar ppt. between sample (may be diluted) and certain concentration of standard solution  similar conc. of reducing sugar

Variables:
 independent variable: conc. of reducing sugars in solutions
 dependent variable: amount of precipitate formed

Others:
 pre-experimental trial: to determine which of the solution (Lucozade or 2% standard glucose solution) with a higher conc. for dilution
 provide a range of solution in different conc. that include the conc. of the other solution.

 assumption:
1. the only reducing agent for precipitate formation in the experiment is reducing sugar in the solutions
2. the gas bubbles contained in Lucozade do not affect the measurement of solution volume.

