Question

How do hydrogen bonds affect solubility?

Answer 1

Hint: We need to know what are hydrogen bonds and study some molecules which are capable of hydrogen bonding and accordingly study their solubility in water. A hydrogen bond is an electrostatic force of attraction between a hydrogen atom covalently bonded to a more electronegative element. They are a type of dipole-dipole interactions which are stronger than van der waals forces but weaker than pure covalent and ionic bonds.

Complete step by step answer:
We know that hydrogen bonding is the bonding between hydrogen and electronegative elements such as $O,F,N$. These bondings are hence polar ; one part of the molecule carries a slightly positive charge and the other part carries a slightly negative charge. This arises due to the difference in electronegativities of the atoms of the molecule. Due to this polarity, they are soluble in water since water is also a polar molecule. Hence $HF$ is readily soluble in water since $F$ is highly electronegative hence highly polar in its hydride form.
Some examples of other polar molecules are $N{H_3}$ ,$C{H_3}OH$ ,$HCl$ etc. One of the best examples to study hydrogen bonding is water. Each water molecule can form four hydrogen bonds with surrounding water molecules and two lone pairs. In comparison to ammonia, there are not enough lone pairs to satisfy all the hydrogens. Therefore, it is true to say that lone pairs are responsible for hydrogen bonding.
Thus, we can conclude that hydrogen bonds highly affect solubility. More polar is the molecule due to hydrogen bonding, higher will be the solubility.

Note:
It must be noted that hydrogen bonding cannot occur without huge electronegativity differences between hydrogen and the atom it is bonded to. These bonds can occur within a molecule (intramolecular) or between two different molecules (intermolecular). The study of the affect of hydrogen bonds to solubility is obviously intermolecular. Also, solubility of less soluble compounds such as carbon-dioxide can be increased by increasing the temperature.