Chemistry Aldehydes & Ketones UHS 2023
PMDC Verified Question 14 of 94
The appearance of a silver mirror in Tollens' test indicates the presence of which of the following?
A
A ketone
B
An aldehyde
C
An acid
D
An alcohol
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: An aldehyde
Concept:

Tollens' reagent (ammoniacal silver nitrate) is the definitive visual test for the formyl group.

Solution:

  • Because aldehydes have a hydrogen atom directly bonded to the carbonyl carbon, they act as reducing agents.


  • They reduce the colorless \( Ag^+ \) complex in Tollens' reagent into solid, metallic \( Ag \).


  • The metallic silver deposits on the glass walls, forming a characteristic "silver mirror."


Why other options are incorrect:

Ketones, carboxylic acids, and alcohols (under these mild basic conditions) lack the necessary reducing power to precipitate silver.

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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