On warming an aldehyde with freshly prepared ammonical silver nitrate solution (Tollen's reagent) a bright silver mirror is produced due to formation of

\(Ag\)

The correct answer is option 1. \(Ag\).

Tollens' reagent is an ammoniacal solution of silver nitrate. It is prepared by dissolving silver nitrate (\(AgNO_3\)) in water and then adding ammonia (\(NH_3\)) until a clear solution forms. This solution contains the complex ion \([Ag(NH_3)_2]^+\), which is the active reagent in the test for aldehydes.

Tollens' Reagent Formula: \([Ag(NH_3)_2]^+\)

Reaction Mechanism

When an aldehyde (\(R-CHO\)) is warmed with Tollens' reagent, it undergoes oxidation, and the silver ion in Tollens' reagent is reduced to metallic silver. The overall reaction can be summarized in two main steps:

Oxidation of Aldehyde:

The aldehyde is oxidized to a carboxylate anion (\(RCOO^-\)).

\(R-CHO + 2[Ag(NH_3)_2]^+ + 3OH^- \rightarrow RCOO^- + 2Ag + 4NH_3 + 2H_2O\)

Here, \(R-CHO\) (the aldehyde) is converted to \(RCOO^-\) (the carboxylate anion).

Reduction of Silver Ions:

The silver ions (\([Ag(NH_3)_2]^+\)) are reduced to metallic silver (\(Ag\)).

\(2[Ag(NH_3)_2]^+ + 3OH^- \rightarrow 2Ag + 4NH_3 + 2H_2O\)

Here, the complex ion \([Ag(NH_3)_2]^+\) loses its silver ions as they get reduced to metallic silver.

Formation of the Silver Mirror

The silver mirror is formed on the inner surface of the test tube due to the reduction of silver ions to metallic silver. This is visually apparent as a shiny, reflective coating.

Detailed Analysis of Options

1. \(Ag\):

Correct. Metallic silver is what forms the mirror-like coating. The silver ion (\(Ag^+\)) in the Tollens' reagent is reduced to metallic silver (\(Ag\)), which deposits as a mirror on the test tube walls.

2. \([Ag(NH_3)_2]^+\):

Incorrect. This is the complex ion present in Tollens' reagent before the reaction. It is not the product responsible for the silver mirror.

3. \(RCOO^-Ag^+\):

Incorrect. This represents a carboxylate ion complex, but it does not describe the actual formation of the silver mirror. The carboxylate ion is formed in the reaction but is not responsible for the mirror.

4. \([R-CHO]Ag\):

Incorrect. This notation does not correctly represent any intermediate or product of the Tollens' test reaction. The aldehyde is oxidized to a carboxylate anion, not directly to a silver complex.

Conclusion
The silver mirror results from the reduction of silver ions (\([Ag(NH_3)_2]^+\)) to metallic silver (\(Ag\)). Therefore, the correct answer is: 1. \(Ag\)