Question

Benedicts reagent is an indicator for the presence of what in a solution?

Answer 1

Reducing sugar and reducing sugar like substances like creatinine,uric acid,homogentisic acid etc.

Explanation:

Benedict's reagent conatins, `CuS0_4,Na-carbonate and Na-citrate`

In presence of alkaline media created due to `Na-carbonate` reducing sugar undergoes ene-diol transformation as a result of this `Cu^(+2)` in `CuSO_4` (blue) gets reduced to `Cu^+` of `Cu_2O` (red).

`Na-citrate` causes slow release of `Cu^(+2)` from `CuSO_4`

So,change in colour of the solution is indicated as a positive test.

Now,this change in color proceeds through a steps of color changes,which corresponds roughly to certain amount of reducing sugar present.

`Blue - 0%`

`Green -0.5 g %`

`Yellow - 1 g%`

`Oran g e - 1.5 g%`

`Red - 2 g%`

`Brick Red - _-^> 2.5 g %`

So,Benedict's test is also called Semiquantitative test.