Account for the following observation:
1)Ammonia is exceptionally soluble in water.
2)Hydrogen fluoride ,HF, has a higher boiling temperature than methane, CH4.
3)The boiling temperature of ammonia (NH3)is -33˚C but that of phosphine (PH3) is -88˚C
1) Ammonia is exceptionally soluble in water due to its ability to form hydrogen bonds. Water molecules have partial positive charges on the hydrogen atoms and partial negative charges on the oxygen atom. Ammonia, NH3, has a lone pair of electrons on its nitrogen atom. When ammonia molecules come into contact with water, the lone pair of electrons of ammonia can form hydrogen bonds with the partially positive hydrogen atoms of water. This interaction between ammonia and water molecules allows ammonia to dissolve easily in water.
2) The higher boiling temperature of hydrogen fluoride (HF) compared to methane (CH4) can be attributed to the presence of hydrogen bonding in HF. Hydrogen bonding occurs when a hydrogen atom is bonded to a highly electronegative atom (such as fluorine, oxygen, or nitrogen) and forms a weak attraction with another electronegative atom of a neighboring molecule. In HF, the hydrogen atom forms a hydrogen bond with the fluorine atom, resulting in additional intermolecular forces that hold the molecules together. These intermolecular forces require more energy to break, leading to a higher boiling temperature for HF compared to CH4, which only exhibits weaker London dispersion forces between its nonpolar molecules.
3) The difference in the boiling temperatures of ammonia (NH3) and phosphine (PH3) can be attributed to the difference in their molecular structures and intermolecular forces. Ammonia molecules are polar, with a central nitrogen atom bonded to three hydrogen atoms, giving it a trigonal pyramidal shape. The presence of the lone pair of electrons on the nitrogen atom allows for the formation of hydrogen bonds between ammonia molecules. On the other hand, phosphine molecules (PH3) are nonpolar and have a trigonal pyramidal shape similar to ammonia. However, phosphine lacks a highly electronegative atom, like nitrogen in ammonia, that can form hydrogen bonds. Instead, phosphine molecules primarily exhibit weaker London dispersion forces between their nonpolar molecules. As a result, ammonia has a higher boiling temperature (-33˚C) compared to phosphine (-88˚C) due to the presence of stronger hydrogen bonds in ammonia, which require more energy to overcome during boiling.