Question

On heating an aldehyde with Fehling’s reagent, a reddish-brown precipitate is obtained due to the formation of

• A. cupric oxide
• B. cuprous oxide
• C. carboxylic acid
• D. silver
• E. copper acetate

Hint:

Fehling's test is used to identify aldehydes by the formation of a reddish-brown precipitate of cuprous oxide.

Answer 1

The Correct Option is B

Fehling’s reagent is a solution of copper(II) sulfate \((CuSO_4)\), sodium hydroxide (NaOH), and potassium sodium tartrate. It is commonly used to test for the presence of aldehydes. When an aldehyde is heated with Fehling’s reagent, the aldehyde is oxidized, and the copper(II) ions \(Cu^2+\) in the reagent are reduced to copper(I) ions \(Cu^+\), forming a reddish-brown precipitate of cuprous oxide \(Cu_2O\). 
The reaction can be summarized as: \[ RCHO + 2[Cu^{2+}] + 4OH^- \rightarrow RCOOH + Cu_2O(s) + 2H_2O \] 
Thus, the reddish-brown precipitate obtained is due to the formation of cuprous oxide \(Cu_2O\). 
Thus, the correct answer is \( \boxed{{cuprous oxide}} \), corresponding to option (B).