Tollen's reagent is

Options

A. Aqueous copper sulphate
B. Alkaline sodium potassium tartarate
C. Ammoniacal silver nitrate
D. Ammoniacal silver chloride

Answer

### Step-by-Step Solution:

1. **Definition of Tollen's Reagent**:
Tollen's reagent is a chemical reagent used to detect the presence of aldehydes. It is specifically an alkaline solution of ammoniacal silver nitrate.

2. **Chemical Composition**:
The chemical formula for Tollen's reagent is Ag(NH₃)₂OH. This indicates that it contains silver ions (Ag⁺) complexed with ammonia (NH₃) and hydroxide ions (OH⁻).

3. **Functionality**:
Tollen's reagent is primarily used in the Tollen's test, which is a qualitative test for aldehydes. When an aldehyde is present, it can reduce the silver ions in Tollen's reagent to metallic silver.

4. **Reaction Mechanism**:
When an aldehyde (RCHO) reacts with Tollen's reagent, it gets oxidized to a carboxylic acid (RCOOH), and the silver ions (Ag⁺) are reduced to metallic silver (Ag). The overall reaction can be summarized as:
\[ RCHO + 2Ag^+ + 2OH^- \rightarrow RCOOH + 2Ag + 2H_2O \]

5. **Conclusion**:
Based on the above information, the correct identification of Tollen's reagent is that it is ammoniacal silver nitrate (Ag(NH₃)₂OH).

### Final Answer:
Tollen's reagent is ammoniacal silver nitrate (Ag(NH₃)₂OH).

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