Which of the following reduces Tollen's reagent ?

Options

A. Acetic acid
B. Citric acid
C. Oxalic acid
D. Formic acid

Answer

To determine which of the given compounds reduces Tollen's reagent, we need to identify the presence of aldehyde functional groups in the compounds listed. Tollen's reagent is specifically used to test for aldehydes, as it can oxidize them while being reduced itself, resulting in the formation of a silver mirror.

### Step-by-Step Solution:

1. **Identify the Compounds**: The question provides a list of compounds. We need to analyze each one to see if it contains an aldehyde group (–CHO).

2. **Analyze Acetic Acid (CH₃COOH)**:
- Acetic acid is a carboxylic acid and has the structure CH₃C(=O)OH.
- It does not contain an aldehyde group.
- **Conclusion**: Acetic acid does not reduce Tollen's reagent.

3. **Analyze Citric Acid**:
- Citric acid is a larger structure and is a tricarboxylic acid with multiple carboxyl groups.
- It does not contain an aldehyde group.
- **Conclusion**: Citric acid does not reduce Tollen's reagent.

4. **Analyze Oxalic Acid (C₂H₂O₄)**:
- Oxalic acid is also a carboxylic acid with the structure HOOC-COOH.
- It does not contain an aldehyde group.
- **Conclusion**: Oxalic acid does not reduce Tollen's reagent.

5. **Analyze Formic Acid (HCOOH)**:
- Formic acid has the structure HCOOH, which can also be represented as HCHO (the aldehyde form).
- It contains an aldehyde group (–CHO) and can reduce Tollen's reagent.
- **Conclusion**: Formic acid does reduce Tollen's reagent.

6. **Final Answer**: Based on the analysis, the compound that reduces Tollen's reagent is **formic acid (HCOOH)**.

### Summary of Findings:
- Acetic acid: No reduction
- Citric acid: No reduction
- Oxalic acid: No reduction
- Formic acid: Yes, reduces Tollen's reagent