abnormal molar mass

Question

When acetic acid is dissolved in benzene, the observed molar mass is approximately twice the expected value. This is due to:

RankGuru · Accepted Answer

In non-polar solvents like benzene, carboxylic acids (like **Acetic acid**) tend to form dimers.
- **Mechanism**: The molecules undergo **Association** through inter-molecular hydrogen bonding.
- Reaction: $2CH_3COOH ightleftharpoons (CH_3COOH)_2$
- Because two molecules combine to form one, the total number of particles decreases. Colligative properties (which depend on particle count) are halved, leading to an **observed molar mass** that is **double** (twice) the actual molecular weight of $60 	ext{ g/mol}$.

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abnormal molar mass

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