Question

Assertion (A) : All aliphatic aldehydes give a positive Fehling’s test.
Reason (R) : Aliphatic aldehydes are reduced by Fehling’s reagent.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Aldehydes are reducing agents; they lose electrons and are oxidized.
Fehling's reagent is an oxidizing agent; it gains electrons and is reduced.
Note that aromatic aldehydes (like benzaldehyde) do not give a positive Fehling's test.

Answer 1

The Correct Option is C

Step 1: Check the Assertion.
Aliphatic aldehydes do turn Fehling's solution positive, giving a brick-red precipitate of $\text{Cu}_2\text{O}$. This happens because the aldehyde is easily oxidised to a carboxylate ion. So the Assertion is true.
Step 2: Check the Reason carefully.
The Reason claims the aldehyde is reduced by Fehling's reagent. In this reaction it is the other way round: the aldehyde is oxidised, it loses electrons and gains an oxygen, while the $\text{Cu}^{2+}$ in the reagent is reduced to $\text{Cu}^+$.
Step 3: Decide if the Reason can still be true in some other sense.
Since the aldehyde is the species being oxidised, not reduced, the statement in the Reason directly contradicts the actual chemistry, so it cannot be accepted as true.
Step 4: Combine the two findings.
The Assertion is a correct fact, but the Reason describes the wrong direction of electron transfer, so it is false.
\[ \boxed{\text{A is true, R is false}} \]