Finding the Concentration of Glucose

Question 1

Benedict’s solution can be used to carry out a semi-quantitative(a result give range for substance being tested) test on a reducing sugar solution to determine

Answer 1

the concentration of reducing sugar present in the sample

Question 2

semi-quantitative

Answer 2

(a result give range for substance being tested)

Question 3

It is important that an excess of Benedict’s solution is used so

Answer 3

hat there is more than enough copper (II) sulfate present to react with any sugar present

Question 4

The intensity of any colour change seen relates to the concentration of reducing sugar present in the sample what colours are which concentration

Answer 4

A positive test is indicated along a spectrum of colour from green (low concentration) to brick-red (high concentration of reducing sugar present)

Question 5

A semi-quantitative test can be carried out by setting up

Answer 5

standard solutions with known concentrations of a reducing sugar (such as glucose)

Question 6

These solutions should be set up using a

Answer 6

serial dilution of an existing stock solution

Question 7

Each solution is then treated in the same way:

Answer 7

add the same volume of Benedict’s solution to each sample and heat in a water bath that has been boiled (ideally at the same temperature each time) for a set time (5 minutes or so) to allow colour changes to occur

It is important to ensure that an excess of Benedict’s solution is used

mix

Question 8

The same procedure is carried out on a sample with an unknown concentration of reducing sugar which is then compared to the

Answer 8

stock solution (dilution series) colours to estimate the concentration of reducing sugar present

Question 9

Alterations
It is also possible to standardise this test but instead of waiting a fixed amount of time for a range of colours to be observed, time how long it takes

why is this also more efficent than measuring out exact measurement of solution

Answer 9

for the first colour change to occur (blue to green)
The higher the concentration of reducing sugar in a sample, the less time it would take for a colour change to be observed

more accurate to use dilution series

Question 10

To avoid issues with human interpretation of colour, a

Answer 10

colourimeter could be used to measure the absorbance or transmission of light through the sugar solutions of known concentration to establish a range of values that an unknown sample can be compared against a calibration curve

Question 11

make dilution series

Answer 11

by adding a 1 part of the 100% conc and 9 parts water then do this over and over or you can do it other ways to get diff concs