Tollen's reagent is

Options

A. `Cu_(2)O`
B. `[Cu(OH)_(4)]^(2-)`
C. `Ag_(2)O`
D. `[Ag(NH_(3))^(2)]^(+)`

Answer

**Step-by-Step Solution:**

1. **Definition of Tollen's Reagent**:
Tollen's reagent is a chemical reagent used to test for the presence of aldehydes. It is a solution of silver nitrate (AgNO3) in ammonia (NH3).

2. **Chemical Composition**:
The chemical formula for Tollen's reagent can be represented as [Ag(NH3)2]+. This indicates that the silver ion (Ag+) is complexed with two ammonia molecules, forming a complex ion.

3. **Preparation**:
To prepare Tollen's reagent, silver nitrate is dissolved in water, and then ammonia is added until the solution becomes clear. It is important to add ammonia slowly to avoid the formation of precipitates.

4. **Functionality**:
Tollen's reagent is primarily used to distinguish between aldehydes and ketones. Aldehydes can reduce Tollen's reagent, resulting in the deposition of metallic silver, which appears as a silver mirror on the inner surface of the test tube.

5. **Reaction with Aldehydes**:
When an aldehyde is present, it reacts with Tollen's reagent to form a carboxylic acid. The general reaction can be represented as:
\[ RCHO + 2[Ag(NH3)2]^+ + 3OH^- \rightarrow RCOO^- + 2Ag + 4NH3 + 2H2O \]
Here, RCHO represents the aldehyde, and RCOO^- is the resulting carboxylate ion.

6. **Distinction from Ketones**:
Ketones do not react with Tollen's reagent under normal conditions, which is why this reagent is useful for distinguishing between these two classes of compounds.

**Final Answer**: Tollen's reagent is ammoniacal silver nitrate, represented as [Ag(NH3)2]+, and is used to differentiate between aldehydes and ketones.

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