On warming an aldehyde with freshly prepared ammoniacal silver nitrate solution (Tollens’ reagent) a bright silver mirror is produced due to formation of
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \(Ag\)
Tollens’ reagent is the diamminesilver(I) complex, \( \ce{[Ag(NH3)2]+} \), in alkaline solution. An aldehyde reduces \( \ce{Ag+} \) to metallic silver, which deposits on the inner wall of the test tube as a bright silver mirror, while the aldehyde is oxidised to the carboxylate anion:
\( \displaystyle \ce{RCHO + 2[Ag(NH3)2]^+ + 3OH^- -> RCOO^- + 2Ag v + 2H2O + 4NH3} \)
Why the other options are incorrect
Option (2) \([Ag(NH_3)_2]^+\) — Incorrect. This is the reagent itself, a colourless soluble complex; it is used up, not formed.
Option (3) \(RCOO^-Ag^+\) — Incorrect. The carboxylate stays in solution as an ion; a silver salt would not give a shiny metallic film.
Option (4) \([R-CHO]Ag\) — Incorrect. No such compound is formed; the aldehyde is oxidised, not bound to silver.
NCERT (2026-27 edition):
Tollens’ Test – “On warming an aldehyde with freshly prepared ammoniacal silver nitrate solution (Tollens’ reagent), a bright silver mirror is produced due to the formation of silver metal. The aldehydes are oxidised to corresponding carboxylate anion. The reaction occurs in alkaline medium.”