A hydrogen bond forms between a hydrogen bond donor (hydrogen) and a hydrogen bond acceptor (nitrogen, oxygen, or fluorine). The strength of a hydrogen bond can be determined by examining the acidity of the hydrogen and basicity of the acceptor. A hydrogen is more acidic when it is attached to a more electronegative atom. This occurs because the electronegative atom pulls the electron density towards itself, making it easy for the hydrogen to act as a leaving group (weaker bond).

A hydrogen on fluorine is the most acidic, and a hydrogen on nitrogen is the least acidic (of the hydrogen bonging possibilities). Basicity of the acceptor is also important in determining the strength of hydrogen bond. A more basic molecule will make the hydrogen bond stronger. Nitrogen forms the strongest hydrogen bonds, whereas fluorine forms the weakest hydrogen bonds.

In our case, the strongest bond will occur between the hydrogen from the hydroxyl group of methanol (most acidic donor) and the nitrogen from ammonia (most basic acceptor).

Hydrogen bonding is an intermolecular force that occurs between a hydrogen bond donor (hydrogen) and a hydrogen bond acceptor (nitrogen, oxygen, or fluorine). The bond is a result of the electromagnetic attraction of the partial positive charge on the hydrogen atom to the partial negative charge on nitrogen, oxygen, and fluorine.

To answer this question you need to look at the chemical makeup of each molecule and determine if the molecule contains the appropriate atoms. Methanol contains oxygen and hydrogen; therefore, methanol molecules can form hydrogen bonds. Dichloromethane and propane contain hydrogen, but they don’t contain nitrogen, oxygen, or fluorine; therefore, they can’t form hydrogen bonds.

"Inter-" means between and "intra-" means within. Intermolecular forces are forces that exist between separate molecules and intramolecular forces exist within or inside a single molecule.

Remember that boiling point and melting point depend on the intermolecular forces, not intramolecular forces. Boiling and melting involve separation of molecules from one another. You will need a higher boiling and melting point if the forces between the molecules (intermolecular forces) are strong. The strongest form of intermolecular force is the hydrogen bond. Hydrogen bonds are intermolecular forces that occur between a hydrogen atom in one molecule and a nitrogen, oxygen, or fluorine atom on another molecule. The molecule with the highest boiling point will have the greatest amount of hydrogen bonds, since this would result in the strongest intermolecular interactions.

Covalent bonds are bonds within the molecule (intramolecular forces) and do not have any effect on the boiling point. Hydrogen bonds can form within a molecule, generating intramolecular forces, but will only do so under certain conditions. The formation of intramolecular hydrogen bonds will not affect boiling point unless the ability to form intermolecular hydrogen bonds is inhibited by this process.

All options have hydrogen attached to an electronegative atom. This difference in electronegativity gives hydrogen a partially positive charge, which allows it to become attracted to neighboring molecules with partially negative charges. This intermolecular force is called hydrogen bonding, and takes place when hydrogen is attached to nitrogen, oxygen, or fluorine.

Fluorine is the most electronegative atom out of the options, meaning that the hydrogen has the strongest partially positive charge in hydrofluoric acid. As a result, it will have the strongest attraction to neighboring molecules. Larger intermolecular forces generally result in higher boiling points. This strong attraction gives it the highest boiling point.

Hydrogen sulfide is the only given compound that does not exhibit hydrogen bonding. This means it will have the weakest intermolecular interactions and, as expected, this results in the lowest boiling point of the given compounds.

Hydrogen bonds are only formed between molecules with polar covalent bonds, and not in nonpolar moelcules. They result from the electromagnetic attraction between hydrogen (which is slightly positively charged) and an atom of opposite (negative) charge, namely the negatively charged end of a polar molecule. All the other statements are accurate.