The molecular mass of acetic acid dissolved in water is 60 and when dissolved in benzene it is 120. This difference in behaviour of `CH_(3)COOH` is because

Options

A. Water prevents association of acetic acid
B. Acetic acid does not fully dissolve in water
C. Acetic acid fully dissolves in benzene
D. Acetic acid does not ionize in benzene

Answer

To solve the question regarding the difference in behavior of acetic acid (CH₃COOH) when dissolved in water versus benzene, we need to analyze the molecular interactions in both solvents.

### Step-by-Step Solution:

1. **Understanding Acetic Acid**:
Acetic acid (CH₃COOH) can behave differently depending on the solvent it is dissolved in. Its molecular mass is given as 60 g/mol when dissolved in water and 120 g/mol when dissolved in benzene.

2. **Dissociation in Water**:
- When acetic acid is dissolved in water, it undergoes dissociation. This means that the acetic acid molecules break apart into ions:
\[ \text{CH}_3\text{COOH} \rightarrow \text{CH}_3\text{COO}^- + \text{H}^+ \]
- In this process, the effective molecular mass observed in solution is lower than the actual molecular mass due to the formation of ions. The molecular mass of the dissociated form is less than 60 g/mol.

3. **Behavior in Benzene**:
- When acetic acid is dissolved in benzene, it does not dissociate. Instead, acetic acid molecules tend to associate with each other due to intermolecular hydrogen bonding, forming dimers:
\[ 2 \text{CH}_3\text{COOH} \rightarrow \text{(CH}_3\text{COOH)}_2 \]
- The molecular mass of this dimer is 120 g/mol (2 × 60 g/mol), which explains why the observed molecular mass in benzene is higher.

4. **Conclusion**:
- The difference in behavior of acetic acid in water and benzene can be attributed to the fact that water promotes dissociation (leading to a lower effective molecular mass), while benzene promotes association (leading to a higher effective molecular mass).

### Final Answer:
The difference in behavior of acetic acid when dissolved in water (60 g/mol) versus benzene (120 g/mol) is because water prevents the association of acetic acid, allowing it to dissociate into ions.