Which among the following alkane has the highest melting point?

Options

A. n-Pentane
B. n-Hexane
C. n_Heptane
D. n-Octane

Answer

To determine which alkane has the highest melting point among the options provided, we can follow these steps:

### Step 1: Understand the Factors Affecting Melting Point
The melting point of alkanes is influenced by several factors:
- **Symmetry**: More symmetrical molecules tend to have higher melting points.
- **Number of Carbon Atoms**: Alkanes with more carbon atoms generally have higher melting points.
- **Odd vs. Even Number of Carbon Atoms**: Alkanes with an even number of carbon atoms usually have higher melting points than those with an odd number of carbon atoms.

### Step 2: Analyze the Given Alkanes
Let's consider the alkanes mentioned:
- **n-Pentane** (C5H12) - 5 carbon atoms (odd)
- **n-Hexane** (C6H14) - 6 carbon atoms (even)
- **n-Heptane** (C7H16) - 7 carbon atoms (odd)
- **n-Octane** (C8H18) - 8 carbon atoms (even)

### Step 3: Apply the Factors
1. **Symmetry**: All the given alkanes are n-alkanes, which means they are linear and symmetrical. Thus, symmetry does not help us differentiate their melting points.
2. **Odd vs. Even Carbon Atoms**:
- n-Pentane and n-Heptane have odd numbers of carbon atoms, which typically results in lower melting points.
- n-Hexane and n-Octane have even numbers of carbon atoms, which typically results in higher melting points.
3. **Number of Carbon Atoms**: Among n-Hexane and n-Octane, n-Octane has more carbon atoms (8) compared to n-Hexane (6), which suggests that n-Octane would have a higher melting point.

### Step 4: Conclusion
Based on the analysis, n-Octane (C8H18) has the highest melting point among the given options.

### Final Answer
The alkane with the highest melting point is **n-Octane (C8H18)**.

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