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NEET CHEMISTRYHydrocarbonsEasy

Question

Given below are two statements: Statement I: The boiling point of three isomeric pentanes follows the order, n-Pentane > Isopentane > Neopentane. Statement II: When branching increases, the molecule attains the shape of a sphere. This results in smaller surface area for contact, due to which the intermolecular forces between the spherical molecules are weak, thereby lowering the boiling point.

A

Both Statement I and Statement II are incorrect.

B

Statement I is correct but Statement II is incorrect.

C

Statement I is incorrect but Statement II is correct.

D

Both Statement I and Statement II are correct.

Step-by-Step Solution

According to the NCERT text, the boiling point of alkanes decreases with an increase in branching. For the isomeric pentanes, n-pentane has a continuous chain of five carbon atoms and the highest boiling point (309.1 K), while the highly branched neopentane (2,2-dimethylpropane) has the lowest (282.5 K), making the order n-Pentane > Isopentane > Neopentane correct . With an increase in the number of branched chains, the molecule attains the shape of a sphere. This results in a smaller area of contact and therefore weak intermolecular van der Waals forces between the spherical molecules, which are overcome at relatively lower temperatures, thereby lowering the boiling point . Therefore, both Statement I and Statement II are true.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Hydrocarbons. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYHydrocarbonsstatementsstatementboilingisomericpentanes

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