Question

Fehling solution A consists of an aqueous solution of copper sulphate, while Fehling solution B consists of an alkaline solution of sodium potassium tartrate.
If the above statement true enters 1, else enters 0.

Answer 1

Hint: Fehling's solution is used to distinguish aldehyde and ketone functional groups present in the organic compounds. A small amount of organic compound is added to Fehling's solution and the resulting mixture is heated. If the organic compound contains aldehyde functional then we can observe the formation of a brick-red color precipitate.

Complete answer:
We know that there are two solutions for Fehling’s test. One solution is called Fehling’s A and the other one is called Fehling’s B.
We have to prepare Fehling’s solution freshly in the laboratory to test the presence of aldehyde functional groups in the organic compounds.
Fehling’s A is a blue color aqueous solution containing copper sulphate.
Fehling’s B is a colorless solution containing sodium potassium tartrate (also called Rochelle salt) and an alkaline solution of sodium hydroxide.
That means after mixing both the solutions only we will get Fehling's test done.
\[RCHO\xrightarrow{Fehling's\text{ }solution}RCOOH+\underset{\operatorname{Re}d\text{ }ppt}{\mathop{C{{u}_{2}}O}}\,\]
Therefore Fehling solution A consists of an aqueous solution of copper sulphate, while Fehling solution B consists of an alkaline solution of sodium potassium tartrate.

So, the given statement is true and we have to enter 1.

Note:
Due to the absence of alpha hydrogens ketones won’t respond to Fehling’s solution. Means ketone won’t give brick-red color precipitate while adding Fehling’s solution. Fehling’s test is one of the most general tests used for the detection of presence of reducing sugars and non-reducing sugars. The benzaldehyde contains an aldehyde functional group but it won’t respond to Fehling’s solution. Because the carbonyl group present in benzaldehyde acts as an electron withdrawing group. It withdraws electrons from the electron-rich benzene ring. So, Fehling's solution is a weaker oxidizing agent and can't oxidize benzaldehyde (it is an aromatic aldehyde).