Question
Which of following observations is found in Tollens test for aldehydes?
MHT CET
Chemistry
Aldehydes and Ketones
2026
MHT CET 2026 (16 April Shift 1)
MHT CET Chemistry Question (2026) — Solution
Options
- A. The formation of pink or magenta color upon the addition of the reagent to the sample solution.
- B. Formation of an Ag layer on sides of test tube upon addition and warming of the reagent.
- C. Formation of brick-red precipitate upon heating with reagent.
- D. Appearance of red color upon shaking with reagent.
Answer
B. Formation of an Ag layer on sides of test tube upon addition and warming of the reagent.
Step-by-step solution
Tollens' reagent is an ammoniacal silver nitrate solution, [Ag(NH_3)_2]^+. When an aldehyde is warmed with Tollens' reagent, the aldehyde is oxidized to the corresponding carboxylate ion, while the silver ions are reduced to metallic silver. RCHO + 2[Ag(NH_3)_2]^+ + 3OH^- RCOO^- + 2Ag + 4NH_3 + 2H_2O The metallic silver deposits on the inner walls of the test tube, forming a characteristic silver mirror or an Ag layer. This observation confirms the presence of an aldehyde group. The formation of a pink or magenta color is observed in Schiff's test, and a brick-red precipitate is observed in Fehling's test. Answer: Formation of an Ag layer on sides of test tube upon addition and warming of the reagent.
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