Question

Fehling’s solution consists of two separate alkaline solutions. One of the solution contains $CuS{O_4}$ , the other solution contains:
A.$NaHC{O_3}$
B.$KNa{C_4}{H_4}{O_6}$
C.$KHC{O_3}$
D.${K_2}C{O_3}$

Answer 1

Hint: In organic chemistry sometimes we have to distinguish or we can say to check whether which functional group is present in organic compound, so to perform this function we have various test and Fehling’s test is one of them and the solution used in this test as a reagent is known as Fehling’s solution.

Complete step by step answer:
As we all know, Fehling’s solution is prepared freshly in the lab. Earlier it is present as two solutions in the lab which are named Fehling’s A and Fehling’s B. Fehling’s A is copper sulphate solution which is blue in colour and Fehling’s B is aqueous sodium potassium tartrate ,it is also known as Rochelle salt which is clear and colourless solution.
Fehling’s A= $CuS{O_4}$
Fehling’s B= $KNa{C_4}{H_4}{O_6}$
Fehling A and Fehling B are mixed in equal volumes to get final Fehling’s solution. It is deep blue coloured liquid.
The method to use Fehling’s solution in lab:
Add a sample in the dry test tube, add Fehling's solution in the test tube, keep the test tube in a water bath, note down or record the observations.
The red ppt. in the observation determines that our result is positive and if there is no change in the solution then it indicates the negative result.
Fehling’s solution is mostly used in the identification of aldehyde and ketones. Aldehydes give positive results while ketones give negative results.
Hence option (B) is correct, $KNa{C_4}{H_4}{O_6}$.

Note: Fehling solution is very corrosive in nature, so while performing experiment protective gloves, mask, etc. should be equipped. Contact with liquid causes severe burns and it is corrosive to eyes also.