Chemistry Aldehydes & Ketones SZABMU 2023
PMDC Verified Question 17 of 94
Aldehydes do not give which identification test:
A
2,4 - DNPH test
B
Tollen's test
C
Sodium Nitro Prusside Test
D
Fehling's Solution
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Sodium Nitro Prusside Test
Concept:

Different functional groups respond selectively to specific reagents based on their electronic and structural properties.

Solution:

  • Aldehydes give a positive 2,4-DNPH test (indicating a carbonyl group).


  • Aldehydes give a positive Tollens' and Fehling's test (due to their ease of oxidation).


  • The Sodium Nitroprusside Test, however, is designed to react with the enolate ions specifically generated by ketones (yielding a wine-red/purple color). Aldehydes generally give a negative or non-distinctive result with this reagent.


Why other options are incorrect:

Options A, B, and D are standard, universally taught positive identification tests for aldehydes.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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