Why `n-`Pentane has higher boiling point than isopentane ?

Answer

To understand why n-pentane has a higher boiling point than isopentane, we can break down the explanation into several steps:

### Step 1: Identify the Structures of n-Pentane and Isopentane
- **n-Pentane**: The structure of n-pentane is a straight-chain hydrocarbon with the formula C5H12, which can be represented as CH3-CH2-CH2-CH2-CH3.
- **Isopentane**: Isopentane, also known as 2-methylbutane, has a branched structure with the formula C5H12, represented as CH3-CH(CH3)-CH2-CH3.

### Step 2: Understand the Concept of Boiling Point
- The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure. It is influenced by the intermolecular forces present in the substance.

### Step 3: Compare the Intermolecular Forces
- In n-pentane, the straight-chain structure allows for more surface area contact between molecules. This increases the strength of the Van der Waals forces (dispersion forces) between the molecules.
- In isopentane, the branched structure reduces the surface area contact between molecules, leading to weaker Van der Waals forces.

### Step 4: Relate Surface Area to Boiling Point
- Since n-pentane has a larger surface area due to its straight-chain structure, it has stronger intermolecular forces compared to isopentane.
- Stronger intermolecular forces require more energy (in the form of heat) to overcome, resulting in a higher boiling point for n-pentane.

### Step 5: Conclusion
- Therefore, n-pentane has a higher boiling point than isopentane because the straight-chain structure of n-pentane allows for stronger Van der Waals forces due to increased surface area, while the branched structure of isopentane results in weaker intermolecular forces.

### Summary
In summary, the higher boiling point of n-pentane compared to isopentane is due to the greater surface area and stronger Van der Waals forces in the straight-chain structure of n-pentane.

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