The acid which reduces Fehling solution is

Options

A. Methanoic acid
B. Ethanoic acid
C. Butanoic acid
D. Propanoic acid

Explanation

To determine which acid can reduce Fehling's solution, we need to understand the properties of the acids mentioned and the nature of Fehling's solution.

### Step-by-Step Solution:

1. **Understanding Fehling's Solution**:
Fehling's solution is a mixture of copper(II) sulfate (CuSO₄) and sodium potassium tartrate in a strong alkaline solution. It is used to test for the presence of reducing sugars and aldehydes.

**Hint**: Remember that Fehling's solution contains Cu²⁺ ions, which are reduced to Cu⁺ ions during the reaction.

2. **Identifying the Acids**:
The acids mentioned are:
- Methanoic acid (formic acid, HCOOH)
- Ethanoic acid (acetic acid, CH₃COOH)
- Propanoic acid (C₂H₅COOH)
- Butanoic acid (C₃H₇COOH)

**Hint**: Focus on the functional groups present in each acid.

3. **Analyzing Functional Groups**:
- Methanoic acid has the structure HCOOH, which contains an aldehyde group (–CHO) as part of its structure.
- Ethanoic acid, propanoic acid, and butanoic acid do not contain an aldehyde group; they contain carboxylic acid groups (–COOH) only.

**Hint**: Aldehyde groups are key to reducing Fehling's solution.

4. **Reactivity with Fehling's Solution**:
The aldehyde group in methanoic acid can reduce Cu²⁺ ions in Fehling's solution to form a red precipitate of cuprous oxide (Cu₂O). This is because aldehydes are reducing agents.

**Hint**: Recall that only compounds with aldehyde groups can reduce Fehling's solution.

5. **Conclusion**:
Since methanoic acid is the only acid among the options that contains an aldehyde group, it is the only acid that can reduce Fehling's solution.

**Final Answer**: The acid which reduces Fehling's solution is **methanoic acid (formic acid)**.