Question detail
Which statement best describes the relationship between the boiling point of an alkane and its carbon chain length in crude oil fractions?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Alkanes
Question
- A. Boiling point decreases as chain length increases
- B. Boiling point is independent of chain length
- C. Boiling point increases as chain length increases
- D. Boiling point first increases then decreases with chain length
Answer
Boiling point increases as chain length increases
Explanation
Longer alkane chains have more London dispersion forces, raising their boiling points; fractional distillation separates fractions accordingly.
Common mistake
Misunderstanding Fractional Distillation
Students often think that fractional distillation separates crude oil based solely on boiling points without considering the role of intermolecular forces.
Fractional distillation separates crude oil into fractions based on both boiling points and the strength of intermolecular forces. The formula for separation involves understanding that components with lower boiling points and weaker intermolecular forces vaporize first. For example, lighter fractions like gasoline have lower boiling points than heavier fractions like diesel. Therefore, as the crude oil is heated, the lighter fractions rise and condense at different levels in the fractionating column.
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