Question

Honey is made from a mixture of fructose, glucose, and sucrose. How can you use Benedict's reagent to determine the number of moles of sucrose in a 1.0g sample of honey? (Hint: If excess Cu2+ is present the difference in [Cu2+] before and after reaction is twice the concentration of reducing sugar present.)

Answer 1

Benedict's reagent is used to determine the quantity of reducing sugar in Honey which is made from a mixture of fructose, glucose, and sucrose

Out of these three sugars Sucrose is an example of a non-reducing sugar which does not react with Benedict's reagent.

While fructose, and glucose are reducing sugar which not react with Benedict's reagent

But when Sucrose is heated with dil HCl it breaks into fructose, and glucose and will give Benedict's test.

Now to determine the number of moles of sucrose in a 1.0g sample of honey we will do titration twice.

Cold condition

Hot with Dil HCl condition

In cold condition Benedict's reagent reacts only the reducing sugars fructose and glucose, while in the hot condition it will reacts sucrose which broken into the reducing sugars ;fructose and glucose also reacts.

Or we can say that this will give you the total amount of sugars present. The difference between the two results is the amount of sucrose present.