The Benedict’s test for reducing sugars

Question 1

Benedict’s test is for

Answer 1

reducing sugars

Question 2

What is benedict’s reagent

Answer 2

is a blue solution that contains copper (II) sulfate ions (CuSO4 ); in the presence of a reducing sugar copper (I) oxide forms

Question 3

Copper oxide is not soluble so it forms

Answer 3

so it forms a precipitate

Question 4

First steps of benedict’s test Add Benedict’s reagent (which is blue as it contains copper (II) sulfate ions) to a sample solution in a test tube heat the……..

Answer 4

Heat the test tube in a water bath or beaker of water that has been brought to a boil for a few minutes

Question 5

What happens if a reducing sugar is present

Answer 5

If a reducing sugar is present, a coloured precipitate will form as copper (II) sulfate is reduced to copper (I) oxide which is insoluble in water

Question 6

Why is it important to put a excess of benedict’s solution

Answer 6

It is important that an excess of Benedict’s solution is used so that there is more than enough copper (II) sulfate present to react with any sugar present

Question 7

A positive test result is a

Answer 7

colour change somewhere along a colour scale from blue (no reducing sugar), through green, yellow and orange (low to medium concentration of reducing sugar) to brown/brick-red (a high concentration of reducing sugar)

Question 8

Why is this test semi quantative

Answer 8

This test is semi-quantitative as the degree of the colour change can give an indication of how much (the concentration of) reducing sugar present

Question 9

What are the reducing sugars

Answer 9

galactose

fructose

glucose

maltose

Question 10

non reducing sugars

Answer 10

sucrose