Textbook Question
Predict which compound in each pair has the higher boiling point. Explain your prediction.
(e)
(f)
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2. Molecular Representations
Intermolecular Forces
2:30 minutesProblem 10a
Textbook Question
List each set of compounds in order of increasing boiling point.
a. hexane, octane, and decane
Verified step by step guidance1
Understand that boiling point is influenced by molecular weight and intermolecular forces. In alkanes, as the molecular weight increases, the boiling point generally increases due to stronger van der Waals forces.
Identify the molecular formula for each compound: hexane (C₆H₁₄), octane (C₈H₁₈), and decane (C₁₀H₂₂).
Recognize that these compounds are all alkanes, which are nonpolar and primarily exhibit van der Waals forces. The longer the carbon chain, the greater the surface area for these forces, leading to a higher boiling point.
Compare the molecular weights: hexane has the lowest molecular weight, followed by octane, and then decane, which has the highest molecular weight.
Arrange the compounds in order of increasing boiling point based on their molecular weights: hexane < octane < decane.
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Video duration:
2mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Boiling Point
Boiling point is the temperature at which a substance transitions from a liquid to a gas. It is influenced by molecular weight, intermolecular forces, and molecular structure. In organic compounds, longer carbon chains typically result in higher boiling points due to increased van der Waals forces.
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Intermolecular Forces
Intermolecular forces are the forces that hold molecules together, affecting properties like boiling point. In hydrocarbons, van der Waals forces (dispersion forces) are predominant. These forces increase with molecular size, leading to higher boiling points for larger molecules.
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Molecular Size and Structure
Molecular size and structure significantly impact boiling points. In alkanes, as the number of carbon atoms increases, the molecular size grows, enhancing van der Waals forces. Thus, among hexane, octane, and decane, decane has the highest boiling point due to its larger size.
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