Explain in terms of forces between structural units why H2O2 has a higher melting point than C3H8. Also, which between the two examples has a lower boiling point?
NH3 or AsH3
C3H7OH or C2H5OCH3
Can you possibly give me a good website that simply explains hydrogen bonding/chemistry in general?
To understand why H2O2 (hydrogen peroxide) has a higher melting point than C3H8 (propane), we need to consider the forces between their structural units.
H2O2 has a higher melting point due to the presence of hydrogen bonding. Hydrogen bonding occurs when the hydrogen atom of one molecule interacts with the highly electronegative atom (e.g., oxygen or nitrogen) of another molecule. In hydrogen peroxide, each oxygen atom forms hydrogen bonds with two neighboring hydrogen peroxide molecules. These hydrogen bonds create strong intermolecular forces that require more energy to break, resulting in a higher melting point for H2O2.
On the other hand, C3H8 consists of nonpolar covalent bonds between carbon and hydrogen atoms, which only experience weaker van der Waals forces (London dispersion forces). These forces are comparatively weaker than hydrogen bonding and thus contribute to a lower melting point for C3H8.
As for the comparison between NH3 (ammonia) and AsH3 (arsine), NH3 has a higher boiling point due to the presence of hydrogen bonding. NH3 molecules can form hydrogen bonds with each other, while AsH3 lacks this capability. Hydrogen bonding results in stronger intermolecular forces in NH3, requiring higher temperatures to break these bonds and allowing for a higher boiling point.
For the comparison between C3H7OH (isopropyl alcohol) and C2H5OCH3 (ethyl methyl ether), C3H7OH has a higher boiling point. This is primarily because C3H7OH can form hydrogen bonds between the hydroxyl (-OH) groups, while C2H5OCH3 lacks this ability. Hydrogen bonding, once again, results in stronger intermolecular forces for C3H7OH, leading to a higher boiling point.
Regarding a website that explains hydrogen bonding and chemistry in general, one good online resource is the website of the Royal Society of Chemistry (www.rsc.org). They provide comprehensive information on various chemical topics, including hydrogen bonding. You can navigate through their educational resources, articles, and tutorials to enhance your understanding of chemistry concepts.