The boiling points of ethene and ethane, two hydrocarbons with similar molecular structures, exhibit distinct differences due to their varying structural characteristics, molecular weights, and intermolecular forces. The boiling point of a substance represents the temperature at which its vapor pressure equals the surrounding atmospheric pressure, and it serves as a crucial parameter for understanding the substance’s physical properties and behavior. Comparing the boiling points of ethene and ethane provides insights into the influence of molecular structure and intermolecular interactions on the phase behavior of organic compounds.
Boiling Points of Ethene and Ethane
When discussing the boiling points of ethene (C2H4) and ethane (C2H6), we’re comparing two hydrocarbons from the alkene and alkane families, respectively. Both are colorless gases at room temperature and pressure:
- Ethene is also known as ethylene, a crucial feedstock in the chemical industry.
- Ethane is a significant component of natural gas.
Their structural difference lies in the presence of a double bond between carbon atoms in ethene, while ethane has only single bonds, resulting in distinct physical properties, including their boiling points.
Boiling Point Values
Ethene: -103.7 °C
Ethane: -88.6 °C
Explanation of the Difference
The higher boiling point of ethane compared to ethene primarily stems from two factors:
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Dispersion Forces: Both molecules experience intermolecular dispersion forces due to electron cloud fluctuations. However, ethane, with more electrons, exhibits stronger dispersion forces leading to a higher boiling point.
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Shape and Surface Area: Ethane’s spherical shape gives it a smaller surface area compared to ethene’s planar shape. This results in reduced intermolecular contact and weaker van der Waals forces in ethene, contributing to its lower boiling point.
Factors Influencing Boiling Points
Molecular Mass: Generally, heavier molecules with higher molecular mass have stronger dispersion forces and thus higher boiling points. However, this factor alone cannot fully explain the difference in this case, as ethene (C2H4) has a slightly lower molecular mass than ethane (C2H6).
Molecular Polarity: Polar molecules, with partial positive and negative charges, experience additional dipole-dipole interactions. However, both ethene and ethane are nonpolar molecules, so this factor is not relevant in explaining the difference in their boiling points.
Hydrogen Bonding: Hydrogen bonding is a strong intermolecular force that occurs between molecules containing hydrogen atoms bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine. Neither ethene nor ethane can form hydrogen bonds, so this factor is also not applicable.
Question 1:
Why is the boiling point of ethene different from that of ethane?
Answer:
The boiling point of ethene is lower than that of ethane due to differences in their molecular structures. Ethene has a double bond between the carbon atoms, while ethane has a single bond. The double bond in ethene creates a more compact molecule that is less likely to interact with other molecules through van der Waals forces. As a result, ethene has weaker intermolecular forces than ethane, leading to a lower boiling point.
Question 2:
How does the boiling point of ethene change with pressure?
Answer:
The boiling point of ethene increases with increasing pressure. This is because increasing pressure forces the ethene molecules closer together, increasing the strength of the intermolecular forces between them. As the intermolecular forces become stronger, more energy is required for the molecules to break free and enter the gas phase, leading to a higher boiling point.
Question 3:
What is the relationship between the polarity of ethene and its boiling point?
Answer:
Ethene is a nonpolar molecule, meaning that the electrons are evenly distributed throughout the molecule. This lack of polarity contributes to the weak intermolecular forces between ethene molecules and its low boiling point. Polar molecules, on the other hand, have a more uneven distribution of electrons, resulting in stronger intermolecular forces and higher boiling points.
Hey there, thanks for hanging out with me and nerding out over the boiling points of ethene and ethane. I hope you found this little journey into the world of chemistry both informative and entertaining. If you’ve got any more burning questions about the scientific wonders that surround us, be sure to drop by again. I’m always up for another round of mind-blowing discoveries! Until next time, keep exploring and keep learning.