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:

The correct option is Both Statement I and Statement II are correct.

Explanation:

Analysis of Statement I:
The boiling point of organic compounds, particularly hydrocarbons like alkanes, depends significantly on the strength of intermolecular forces, specifically London dispersion forces (Van der Waals forces). For isomeric alkanes, as the degree of branching increases, the molecular shape becomes more spherical and compact. This reduces the effective surface area of the molecule. Since Van der Waals forces are directly proportional to the surface area of contact, a smaller surface area leads to weaker intermolecular attractions, which in turn lowers the boiling point.
Let us look at the structure and boiling points of the three isomeric pentanes:
1. n-pentane (straight chain): It has a linear structure with a large surface area of contact, leading to strong intermolecular forces. Its boiling point is approximately 309 K (36 °C).
2. isopentane (2-methylbutane, one branch): It is more compact than n-pentane. Its boiling point is approximately 301 K (28 °C).
3. neopentane (2,2-dimethylpropane, two branches): It is highly branched and has a spherical shape with the smallest surface area. Its boiling point is approximately 282.5 K (9.5 °C).
Thus, the boiling point follows the order: n-pentane > isopentane > neopentane. Therefore, Statement I is correct.

Analysis of Statement II:
Branching in a molecule prevents the chains from packing closely together. As branching increases, the molecule is pulled into a more compact shape resembling a sphere. Spheres have the minimum surface area for a given volume. Consequently, the surface area available for contact between adjacent molecules decreases. Since dispersion forces depend on surface-to-surface contact, these intermolecular forces become weaker, requiring less thermal energy to overcome them and transition into the gas phase. This directly explains why the boiling point decreases with branching. Therefore, Statement II is correct.

Since both Statement I and Statement II are correct, the most appropriate choice is that both statements are correct.