Assertion (A): All aliphatic aldehydes give a positive ...

CBSE Class 12 Chemistry 2026 All Sets Solved Paper

Question : 16 of 16

Marks: +1, -0

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

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

Solution:

Assertion (A):
All aliphatic aldehydes give a positive Fehling's test. True.
They reduce Fehling’s solution to give a brick-red precipitate of

Cu_2O

.
Reason (R):
“Aliphatic aldehydes are reduced by Fehling’s reagent.” False.
Actually, aldehydes are oxidized, not reduced.
Aldehyde

\to

oxidized to carboxylate ion

Cu^{2+}

(in Fehling’s solution)

\to

reduced to

Cu_2O

So the aldehyde acts as a reducing agent.

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