This is because \(H_2O\), \(HF\), and \(NH_3\) all exhibit hydrogen bonding, whereas the others do not. We see that \(H_2O\), \(HF\), and \(NH_3\) each have higher boiling points than the same compound formed between hydrogen and the next element moving down its respective group, indicating that the former have greater intermolecular forces. However, when we consider the table below, we see that this is not always the case. Larger molecules have more space for electron distribution and thus more possibilities for an instantaneous dipole moment. This, without taking hydrogen bonds into account, is due to greater dispersion forces. When we consider the boiling points of molecules, we usually expect molecules with larger molar masses to have higher normal boiling points than molecules with smaller molar masses. For example, intermolecular hydrogen bonds can occur between \(NH_3\) molecules alone, between \(H_2O\) molecules alone, or between \(NH_3\) and \(H_2O\) molecules. They can occur between any number of like or unlike molecules as long as hydrogen donors and acceptors are present an in positions in which they can interact. Intermolecular hydrogen bonds: Intermolecular hydrogen bonds occur between separate molecules in a substance.For example, intramolecular hydrogen bonding occurs in ethylene glycol (\(C_2H_4(OH)_2\)) between its two hydroxyl groups due to the molecular geometry. In order for this to happen, both a hydrogen donor an acceptor must be present within one molecule, and they must be within close proximity of each other in the molecule. This occurs when two functional groups of a molecule can form hydrogen bonds with each other. Intramolecular hydrogen bonds: Intramolecular hydrogen bonds are those which occur within one single molecule.Hydrogen bonds can occur within one single molecule, between two like molecules, or between two unlike molecules.
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