Effervescence takes place when sodium carbonate solution is added to

Options

A. formaldehyde
B. acetaldehyde
C. acetic acid
D. phenol

Answer

To determine when effervescence occurs upon the addition of sodium carbonate solution, we need to analyze the given compounds: formaldehyde, acetaldehyde, acetic acid, and phenol.

### Step-by-Step Solution:

1. **Identify the Nature of Sodium Carbonate**:
Sodium carbonate (Na2CO3) is a basic salt that reacts with acids to produce carbon dioxide gas, which is responsible for effervescence.

2. **List the Given Compounds**:
- Formaldehyde: HCHO
- Acetaldehyde: CH3CHO
- Acetic Acid: CH3COOH
- Phenol: C6H5OH

3. **Determine Which Compounds are Acids**:
- Formaldehyde does not have a carboxylic acid group (COOH).
- Acetaldehyde also does not have a carboxylic acid group.
- Acetic acid has a carboxylic acid group (COOH) and is a weak acid.
- Phenol is not a carboxylic acid; it has a hydroxyl group (OH) but does not react like an acid in this context.

4. **Identify the Reaction with Sodium Carbonate**:
The reaction occurs primarily with carboxylic acids. When acetic acid (CH3COOH) reacts with sodium carbonate (Na2CO3), the following reaction takes place:
\[ \text{CH}_3\text{COOH} + \text{Na}_2\text{CO}_3 \rightarrow \text{CH}_3\text{COONa} + \text{CO}_2 + \text{H}_2\text{O} \]
Here, sodium acetate (CH3COONa), carbon dioxide (CO2), and water (H2O) are formed.

5. **Conclusion**:
Since only acetic acid produces carbon dioxide gas when reacted with sodium carbonate, it is the only compound among the given options that will cause effervescence. Therefore, the correct answer is **acetic acid**.

### Final Answer:
Effervescence takes place when sodium carbonate solution is added to **acetic acid**.

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