Let's analyze the given data about four hydrocarbons, each containing one hydrogen bond, and examine their boiling points:
| Compound | Boiling Point (°C) |
|----------|---------------------|
| W | 78.4 |
| X | 64.7 |
| Y | 117.7 |
| Z | 97.1 |
### Analyzing the Possible Causes for Differences in Boiling Points
1. Different Numbers of Oxygen Atoms:
- All the compounds have one hydrogen bond. Since hydrogen bonding typically involves interaction with oxygen (or nitrogen, fluorine), we could consider the number of oxygen atoms. However, it’s not mentioned that differing numbers of oxygen atoms are a factor here.
2. Different Amounts of Dispersion Forces:
- Dispersion forces, also known as London dispersion forces or van der Waals forces, are dependent on the size and shape of the molecules as well as the number of electrons. Larger molecules with more electrons generally have stronger dispersion forces, leading to higher boiling points.
3. Molecules Are Always at Higher Temperature:
- This option is irrelevant to the variations in boiling points. The boiling point is an intrinsic property of the substance under standard atmospheric pressure and doesn’t change due to the typical temperature of the molecules.
### Conclusion
Given the information:
- All compounds have one hydrogen bond, ruling out significant differences in hydrogen bonding.
- The differences in boiling points signify varying intermolecular forces of attraction among the molecules.
Among the given options, the most plausible reason for the differences in boiling points is due to varying dispersion forces. Therefore, Compounds W, X, Y, and Z possess different amounts of dispersion forces, leading to their varied boiling points.
Therefore, the most likely cause for the difference in boiling points of the compounds is:
- The molecules have different amounts of dispersion forces.
Hence, the correct answer is:
- The molecules have different amounts of dispersion forces.
