Ethanol and carbon dioxide have approximately the same molecular weight, yet carbon dioxide is a gas at STP and ethanol is a liquid. How do you account for this difference in physical property?
Ethanol has hydrogen bonds. CO2 does not.
The difference in physical property between carbon dioxide and ethanol can be explained by their molecular structures and intermolecular forces.
Carbon dioxide (CO2) is a linear molecule consisting of one carbon atom bonded to two oxygen atoms. It has a molecular weight of approximately 44 g/mol. Carbon dioxide molecules are arranged in a way that allows for weak intermolecular forces, specifically London dispersion forces, between them.
Ethanol (C2H5OH), on the other hand, has a molecular weight of approximately 46 g/mol and is a larger, more complex molecule. It consists of two carbon atoms, six hydrogen atoms, and one oxygen atom. Ethanol molecules have both London dispersion forces and hydrogen bonding due to the presence of an -OH group.
Hydrogen bonding is a strong intermolecular force that occurs when a hydrogen atom is bonded to a highly electronegative atom (such as oxygen or nitrogen) and is attracted to another electronegative atom in another molecule. The presence of hydrogen bonding in ethanol allows for stronger intermolecular forces than carbon dioxide, resulting in a higher boiling point and it being a liquid at room temperature.
In summary, the difference in physical property between carbon dioxide and ethanol can be attributed to the presence of hydrogen bonding in ethanol, which leads to stronger intermolecular forces and a higher boiling point, allowing it to exist as a liquid at STP, while carbon dioxide, with weaker intermolecular forces, exists as a gas.
The difference in physical property between carbon dioxide (CO2) and ethanol (C2H5OH) can be accounted for by considering their molecular structures and intermolecular forces.
First, let's examine the molecular structures of the two compounds. Carbon dioxide consists of one carbon atom bonded to two oxygen atoms, forming a linear molecule. Ethanol, on the other hand, contains a carbon atom bonded to three hydrogen atoms and an -OH group, resulting in a bent or V-shaped molecule. The presence of the -OH group in ethanol leads to a difference in molecular shape compared to carbon dioxide.
Now, let's consider intermolecular forces, which are the forces between molecules that influence their physical properties. In the case of CO2, the primary intermolecular force is London dispersion forces (also known as van der Waals forces). These forces occur due to temporary fluctuations in electron distribution, leading to the creation of temporary dipoles. These temporary dipoles induce dipoles in neighboring CO2 molecules, resulting in weak attractions between them. Since London dispersion forces increase with increasing molecular mass, CO2 experiences relatively weak intermolecular forces.
In contrast, ethanol exhibits additional intermolecular forces, primarily due to the presence of the -OH group. This -OH group allows ethanol molecules to undergo hydrogen bonding. Hydrogen bonding occurs when a hydrogen atom bonded to an electronegative atom (in this case, oxygen) interacts with another electronegative atom (in ethanol, another oxygen or nitrogen atom). Hydrogen bonds are stronger than London dispersion forces, leading to increased intermolecular attractions in ethanol compared to carbon dioxide.
These additional hydrogen bonding interactions in ethanol result in a stronger molecular attraction and higher boiling point, allowing ethanol to exist as a liquid at room temperature (STP - standard temperature and pressure). In contrast, carbon dioxide lacks the ability to form hydrogen bonds due to its molecular structure, resulting in weaker intermolecular forces. As a result, carbon dioxide remains a gas at STP.
In summary, the difference in physical properties between ethanol and carbon dioxide is mainly due to the presence of hydrogen bonding in ethanol, which leads to stronger intermolecular forces and, consequently, a higher boiling point, allowing ethanol to exist as a liquid at STP.