Question

When a mixture of an aldehyde and Fehling solution is boiled in hot water, a red precipitate is formed. Here the obtained red precipitate is of -

• A. Cuprous oxide
• B. Cupric chloride
• C. Cuprous hydroxide
• D. Cupric sulphate

Hint:

Fehling's test reduces copper(II) to copper(I) oxide, a red-brown solid.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Fehling's solution contains \(\text{Cu}^{2+}\) ions as a tartrate complex in alkaline medium.
Aliphatic aldehydes reduce it on warming.

Step 2: Reaction
The aldehyde is oxidised to a carboxylate ion and \(\text{Cu}^{2+}\) is reduced to \(\text{Cu}^{+}\).
This gives a red-brown precipitate of \(\text{Cu}_{2}\text{O}\).

Step 3: Name the product
\(\text{Cu}_{2}\text{O}\) is copper(I) oxide, which is called cuprous oxide.

Final Answer:
The red precipitate is cuprous oxide, option (A). \[ \boxed{\text{(A) }\text{Cuprous oxide}} \]