Chapter 3: 3.4

Question 1

What test is used to test for reducing sugars?

Answer 1

Benedict’s test

Question 2

What is the Benedict’s reagent?

Answer 2

Alkaline solution of copper(II)sulfate

Question 3

How is the Benedict’s test carried out?

Answer 3

1. Place sample to be tested in a boiling tube. If sample isn’t liquid, grind it up or blend it in water
2. Add equal volume of Benedict’s reagent
3. Gently heat the mixture in a boiling water bath for 5 mins

Question 4

What happens during the test?

Answer 4

• React in Benedict’s reagent

- Electrons then added to the blue copper(II) ions

Question 5

What is the most common non-reducing sugar?

Answer 5

Sucrose

Question 6

How do you test sucrose with Benedict’s?

Answer 6

• Boil sucrose with dilute hydrochloric acid
• This will give a positive result when warmed with Benedict’s solution
• This is because sucrose has been hydrolysed by the acid into glucose and fructose (reducing sugars)

Question 7

What is the Iodine test used to test for?

Answer 7

Starch

Question 8

How is the Iodine test carried out?

Answer 8

1. A few drops of iodine dissolved in potassium iodide solution are mixed with a sample

Question 9

What indicates the presence of starch during the Iodine test?

Answer 9

Solution turns from yellow/brown to purple/black

Solution = remains brown/yellow = negative result - no starch present

Question 10

What are reagent strips used for?

Answer 10

To test for presence of reducing sugars

Question 11

What is the advantage of reagent strips?

Answer 11

Concentration of sugar can be determined with the use of a colour-coded chart

Question 12

What is a colorimeter used for?

Answer 12

To quantitatively measure the absorbance/transmission of light by colored solution
(The more the concentrated the solution is, the less the light will be transmitted)

Question 13

Whatresults of a colorimeter calculate?

Answer 13

Reducing sugar present