test for reducing sugars

Question 1

what is the name of the test for reducing sugars?

Answer 1

benedict’s test

Question 2

what do reducing sugars do?

Answer 2

give electrons

Question 3

what does benedict’s solution contain?

Answer 3

Cu+2 ions which make the solution blue

Question 4

what are examples of reducing sugars?

Answer 4

all monosaccharides and disaccharides except sucrose

Question 5

explain the process of the benedict’s test

Answer 5

• add a small amount (2cm^3) of the sample into a test tube with 2cm^3 of benedict’s solution
• heat in a water bath for 5 minutes
• brick red or orange colour is a positive result and a reducing sugar is present
• if benedict’s solution remains blue , no reducing sugar is present and this is a negative result

Question 6

what state must the sample be in before the benedict’s test is carried out?

Answer 6

it must be a liquid

Question 7

what is the order of colours of the solution from highest concentration of reducing sugar to lowest concentration of reducing sugar?

Answer 7

red, orange, yellow, green

Question 8

what are the controlled variables of this test?

Answer 8

• same volume of benedict’s solution and the same volume of test solutions
• samples must be heated for the same amount of time
• samples must be heated at the same temperature

Question 9

how to accurately compare the colour intensity produced?

Answer 9

with a colorimeter

Question 10

how do you use a colorimeter?

Answer 10

• set up colorimeter to absorb a particular wavelength of light
• calibrate the colorimeter (set the zero concentration mark by measuring the absorbance of a sample of distilled water)
• measure the absorbency of solutions with a known concentration
• produce a calibration curve
• place the solution of an unknown concentration of reducing sugar in the colorimeter
• measure the absorbency and use the calibration curve to determine the concentration