Question detail
Describe how the boiling points of fractions from crude oil change with increasing chain length and explain why this occurs.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Alkanes
Question
Describe how the boiling points of fractions from crude oil change with increasing chain length and explain why this occurs.
Answer
As the chain length of hydrocarbons increases, their boiling points also increase. This is due to the increase in van der Waals forces between the larger molecules, which require more energy to overcome during the transition from liquid to gas.
Explanation
This answer is strong as it clearly explains the trend in boiling points with chain length and provides a rationale based on intermolecular forces. The question assesses the student's ability to articulate the relationship between molecular structure and physical properties in organic chemistry.
Common mistake
Misunderstanding Fraction Properties
Students often confuse the relationship between chain length and boiling point, thinking that longer chains always have lower boiling points.
To clarify, remember that as chain length increases, the boiling point generally increases due to stronger van der Waals forces. For example, consider the formula for boiling point trends: longer chains lead to increased surface area, which enhances intermolecular forces. Thus, longer alkanes have higher boiling points. Always relate this to the strength of intermolecular forces.
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