Why is the boiling point of n-Pentane about 28'C higher than that of its 2,2-Dimethylpropane isomer?
Correct answer: A. The small surface area of 2,2-Dimethylpropane leads to weaker intermolecular forces.
- A. The small surface area of 2,2-Dimethylpropane leads to weaker intermolecular forces.
- B. 2,2-Dimethylpropane molecules experience repulsive forces.
- C. N-Pentane molecules have difficulty interacting closely with each other.
- D. Molecular shape has no impact on boiling point.
Explanation
The correct answer is A. The boiling point of a hydrocarbon is influenced by the strength of intermolecular forces, which depend on molecular shape and surface area. N-Pentane, with its linear structure, has a larger surface area, allowing stronger Van der Waals forces between molecules compared to the more compact, branched shape of 2,2-Dimethylpropane. This results in n-Pentane having a significantly higher boiling point.Options B, C, and D are incorrect because they fail to recognize the influence of molecular shape and surface area on intermolecular forces, which are critical in determining boiling points.
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About Alkanes
Alkanes are saturated hydrocarbons containing only carbon-carbon and carbon-hydrogen single bonds, with the general formula CnH2n+2 for open chains. Their structure, isomerism, IUPAC nomenclature, physical properties, combustion, free-radical halogenation and conformations are covered, including the difference between substitution in alkanes and addition in unsaturated hydrocarbons.
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