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 a shape of 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.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both Statement I and Statement II are correct.
• B. Both Statement I and Statement II are incorrect.
• C. Statement I is correct but Statement II is incorrect.
• D. Statement I is incorrect but Statement II is correct.

Answer 1

The Correct Option is A

Statement I discusses the boiling points of three isomeric pentanes: n-pentane, isopentane, and neopentane. The order mentioned is: n-pentane > isopentane > neopentane. This statement is correct because boiling point is influenced by the surface area available for intermolecular forces. n-Pentane, being a linear molecule, has the largest surface area, resulting in greater van der Waals forces, and thus a higher boiling point compared to its branched isomers.

Statement II explains the effect of branching on the molecule's shape and boiling point. As branching increases, molecules assume a more spherical shape, which minimizes the surface area available for intermolecular interactions like van der Waals forces. This decrease in surface area weakens these forces, thereby reducing the boiling point. This statement correctly explains the molecular behavior and its impact on boiling point.

Since both statements accurately describe the relationship between molecular structure and boiling point, the correct answer is: Both Statement I and Statement II are correct.