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

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:

Explanation:

Statement I:

The boiling points of isomeric alkanes are influenced by their shape and surface area. n-pentane is a straight-chain alkane, isopentane has one branch, and neopentane has a highly branched, nearly spherical shape. The boiling points generally decrease with increased branching due to the reduction in surface area and weaker van der Waals forces. Therefore, the order n-pentane > isopentane > neopentane is correct. Statement I is correct.

Statement II:

As branching increases, the molecule does indeed become more spherical, reducing its surface area. This results in weaker intermolecular forces (van der Waals forces), which in turn lowers the boiling point. Therefore, Statement II is also correct and provides a valid explanation for Statement I

Conclusion:

Both Statement I and Statement II are correct.