Melting Point As Purity Criterion
A pure organic compound has reported melting point 122-123 degC. A laboratory sample melts over 116-121 degC. This observation indicates that the sample is:
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About This Question
- Subject
- chemistry
- Chapter
- purification and characterisation of organic compounds
- Topic
- melting point as purity criterion
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Impure due to lowered and broadened melting range
Impurities usually depress melting point and broaden the melting range because they disrupt crystal lattice regularity. A pure solid melts sharply over a narrow range, often about 1 degC. The observed broad and lower range (116-121 degC) therefore indicates impurity.
This easy difficulty chemistry question is from the chapter purification and characterisation of organic compounds, covering the topic of melting point as purity criterion. It appeared in the 2025 exam.
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