Question

Which one of the following molecules will form a linear polymeric structure due to hydrogen bonding? (a) \(\mathrm{NH}_{3}\) (b) \(\mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{HCl}\) (d) HF

Short answer

(d) HF forms a linear polymeric structure due to hydrogen bonding.

Step-by-step solution

Recognize hydrogen bonding

Identify which molecules can participate in hydrogen bonding. Hydrogen bonding typically occurs in molecules where hydrogen is directly bonded to highly electronegative atoms like nitrogen, oxygen, or fluorine.

Analyze each molecule

- For \(\mathrm{NH}_3\), hydrogen is bonded to nitrogen, allowing for hydrogen bonding.- For \(\mathrm{H}_2O\), hydrogen is bonded to oxygen, allowing for hydrogen bonding.- For \(\mathrm{HCl}\), hydrogen is bonded to chlorine, which is not sufficiently electronegative for significant hydrogen bonding.- For \(\mathrm{HF}\), hydrogen is bonded to fluorine, allowing for strong hydrogen bonding potential.

Determine polymer potential

Consider how each molecule could form extended structures through hydrogen bonding. - \(\mathrm{NH}_3\) can form hydrogen bonds but does not typically form a linear polymeric structure.- \(\mathrm{H}_2O\) forms a network rather than a linear structure due to its bent shape.- \(\mathrm{HCl}\) does not form hydrogen-bonded polymers.- \(\mathrm{HF}\) can form extended, linear structures because each molecule can form hydrogen bonds linearly, with each HF molecule bonding in a chain.

Conclusion

Among the given options, \(\mathrm{HF}\) is the molecule that will form a linear polymeric structure due to hydrogen bonding, as it can form continuous hydrogen-bonded chains.

Key concepts

Polymeric Structure

A polymeric structure is essentially a large molecule composed of repeated smaller units known as monomers. In some cases, these structures can be formed through hydrogen bonding, which is a special type of intermolecular force. When we think about polymers, we often consider that they can form in either a linear or network form.
Linear polymers have chains of monomer units connected end to end. These chains are typically formed through chemical bonding. However, under certain conditions, hydrogen bonding can create similar chain-like structures.
In the context of the molecules given (FHF, FNH_3, FH_2O, FHCl), the formation of a polymeric structure depends on how well these molecules can align and bond repeatedly with each other. HF is unique among these options as it can form a linear polymer because the hydrogen bonds align to form a chain-like structure by constantly bonding with the fluorine of neighboring molecules.

Electronegativity

Electronegativity is the measure of an atom's ability to attract and hold onto electrons within a bond. It plays a critical role in determining the kind and strength of bonds that can occur between atoms.
For hydrogen bonding, electronegativity is especially important. Hydrogen bonds occur when hydrogen is bonded to highly electronegative atoms such as nitrogen, oxygen, or fluorine. These atoms hold the electrons tightly, causing a positive charge on the hydrogen and allowing it to form a bond with another electronegative atom.
In our example molecules, fluorine is the most electronegative, which explains HF's strong hydrogen-bonding ability. As a result, HF can form strong hydrogen bonds that enable the formation of a linear polymeric structure. On the other hand, chlorine in HCl does not have enough electronegativity to facilitate effective hydrogen bonding, which prevents the formation of a linear polymeric structure.

Linear Polymers

Linear polymers are comprised of long, straight chains of monomer units linked together. These polymers are typically flexible and can pack closely together, resulting in different physical properties.
The ability to form linear polymers through hydrogen bonding is rare and requires specific conditions. HF is one of the unique cases where this happens naturally due to the directional nature of hydrogen bonding. The linearity comes from the fact that each HF molecule can potentially bond with the next HF molecule in a line repeatedly.
In other substances like FH_2O, the potential for forming a linear polymer doesn't exist because of the bent shape of the water molecule, which prevents extended alignment. Similarly, in FNH_3, although hydrogen bonding can occur, the overall structural formation is not linear, and thus, they do not form linear polymers as HF does.