Abnormal Molar Mass
Mediumchemistry
When acetic acid is dissolved in benzene, the observed molar mass is approximately twice the expected value. This is due to:
Select the correct option:
Solution
Incorrect! Answer:
Association
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: 2CH3COOH⇌(CH3COOH)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 g/mol.
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About This Question
- Subject
- chemistry
- Chapter
- solutions
- Topic
- abnormal molar mass
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Association
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: 2CH3COOH⇌(CH3COOH)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 g/mol.
This medium difficulty chemistry question is from the chapter solutions, covering the topic of abnormal molar mass. It appeared in the 2025 exam.
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