How does the melting point of propane and ethane compare?

Options

A. The melting point of propane is greater
B. The melting point of ethane is greater
C. The melting points are within `5^@C` of one another
D. No relationship exists among these alkanes and their melting points

Explanation

To compare the melting points of propane and ethane, we can follow these steps:

### Step 1: Identify the Chemical Structures
- **Propane (C3H8)**: It has 3 carbon atoms.
- **Ethane (C2H6)**: It has 2 carbon atoms.

### Step 2: Understand the General Trend in Melting Points of Alkanes
- In alkanes, it is generally observed that alkanes with an even number of carbon atoms tend to have higher melting points than those with an odd number of carbon atoms. This is due to the packing efficiency and intermolecular forces.

### Step 3: Determine the Melting Points
- The melting point of ethane (C2H6) is **-182.8°C**.
- The melting point of propane (C3H8) is **-189.1°C**.

### Step 4: Compare the Melting Points
- Since **-182.8°C** (ethane) is greater than **-189.1°C** (propane), we conclude that ethane has a higher melting point than propane.

### Step 5: Calculate the Difference in Melting Points
- The difference in melting points is calculated as follows:
\[ -182.8°C - (-189.1°C) = -182.8 + 189.1 = 6.3°C \]
- This shows that the melting points differ by **6.3°C**, which is greater than 5°C.

### Conclusion
- Therefore, the correct answer is that the melting point of ethane is greater than that of propane.

### Summary of Options
- A: Melting point of propane is greater - **Incorrect**
- B: Melting point of ethane is greater - **Correct**
- C: Melting points are within 5 degrees Celsius - **Incorrect**
- D: No relationship exists among these alkanes - **Incorrect**

### Final Answer
The melting point of ethane is greater than that of propane.

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