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 composed of a solution of silver nitrate (AgNO3) mixed with ammonia (NH4OH).

2. **Components of Tollen's Reagent:**
- **Silver Nitrate (AgNO3):** This is a common silver salt that is soluble in water.
- **Ammonium Hydroxide (NH4OH):** This is a solution of ammonia in water, which helps to dissolve the silver nitrate and forms a complex ion.

3. **Formation of Tollen's Reagent:**
When silver nitrate is mixed with ammonium hydroxide, a complex ion is formed:
\[ \text{AgNO}_3 + \text{NH}_4\text{OH} \rightarrow \text{[Ag(NH}_3\text{)]}^+ + \text{NO}_3^- \]
This complex ion is what makes Tollen's reagent effective in its function.

4. **Oxidizing Properties:**
Tollen's reagent acts as a mild oxidizing agent. It is specifically known for its ability to oxidize aldehydes to carboxylic acids while reducing the silver ion (Ag+) to metallic silver (Ag), which can be observed as a silver mirror on the inner surface of the test tube.

5. **Reaction with Aldehydes:**
The general reaction can be represented as follows:
\[ \text{RCHO} + 2\text{[Ag(NH}_3\text{)]}^+ + 2\text{OH}^- \rightarrow \text{RCOO}^- + 2\text{Ag} + 2\text{NH}_3 + 2\text{H}_2\text{O} \]
Here, RCHO represents the aldehyde, which gets oxidized to a carboxylate ion (RCOO^-).

6. **Conclusion:**
Tollen's reagent is primarily used in organic chemistry to test for the presence of aldehydes due to its selective oxidation properties.

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