Question

Boric acid is polymeric due to (a) Its geometry (b) Its presence of hydrogen bonds (c) Its acidic nature (d) Its monobasic nature

Short answer

Boric acid is polymeric due to its presence of hydrogen bonds (option b).

Step-by-step solution

Understanding Polymerization

Polymeric substances are those that form large, repeating structures consisting of many similar or identical units bonded together. To determine the reason behind boric acid being polymeric, we need to identify which property facilitates its formation into such repeating structures.

Analyzing the Properties of Boric Acid

Boric acid, with the chemical formula H3BO3, can form extensive hydrogen bonding networks through the hydrogen atoms attached to oxygen and the lone pairs on the oxygen atoms themselves. This allows for connectivity between molecules, leading to a polymeric structure.

Evaluating Each Option

Let's evaluate each option: (a) Geometry - while geometry is important, it does not necessarily lead to polymer formation. (b) Presence of hydrogen bonds - these bonds create the intermolecular connections necessary for polymerization. (c) Acidic nature - this alone doesn't facilitate polymerization directly. (d) Monobasic nature - indicates the basic removal of one hydrogen ion, which is unrelated to polymeric structure.

Selecting the Correct Reason

Given that hydrogen bonds are key to the polymeric nature of boric acid due to their facilitating extensive intermolecular connections, option (b) is the correct reason why boric acid is polymeric.

Key concepts

Hydrogen Bonding

Hydrogen bonding occurs when a hydrogen atom is shared between two electronegative atoms, such as oxygen or nitrogen. This type of bonding is unique because it is significantly stronger than the typical dipole-dipole interaction, yet weaker than covalent bonds.
In the case of boric acid, with the formula H\(_3\)BO\(_3\), each molecule contains hydrogen atoms bonded to oxygen atoms. These hydrogen atoms can form hydrogen bonds with the lone pairs of electrons found on the oxygen of another boric acid molecule.
The oxygen atoms in boric acid are highly electronegative. They attract the shared electrons in the hydrogen bonds, creating a partial negative charge on the oxygen atoms and a partial positive charge on the hydrogen atoms. This polarity facilitates the interaction required for hydrogen bonds.

• This network of hydrogen bonds allows boric acid molecules to connect with each other, crucial for polymerization.
• These bonds contribute to the stability of the entire structure formed by boric acid molecules.

Hydrogen bonding is a critical component in the formation of many biological and synthetic polymers because it provides a flexible and reversible method of holding molecules together.

Polymer Formation

Polymer formation is a process where small molecules, known as monomers, chemically bond to form a large chain or network, referred to as a polymer. In boric acid's case, its polymeric structure arises from hydrogen bonds connecting individual molecules together repeatedly.
Typically, polymers can be natural like cellulose or synthetic like nylon. Although boric acid isn't a polymer in the traditional sense, its network through hydrogen bonding gives it polymeric properties.

In the polymer formation of boric acid:

• Molecules are held together through hydrogen bonds, not traditional covalent bonds seen in classical polymerization.
• No distinct change like breaking or forming of typical covalent bonds during linkage occurs.

The repeating units of connected boric acid molecules create a stable and extensive structure. This network is flexible as these hydrogen bonds can be formed and broken with changes in conditions such as temperature, without altering the fundamental structure of the boric acid molecules themselves.

Intermolecular Connections

Intermolecular connections refer to forces that hold molecules together. In the context of boric acid, these are the hydrogen bonds that create its unique polymeric structure. These connections are weaker than the covalent bonds that hold the atoms within a molecule together but are crucial for the material's structural integrity.
These intermolecular connections in boric acid ensure the creation of a robust network that can distribute forces throughout its structure efficiently.

The significance of these connections includes:

• Enabling the polymer-like property of boric acid without the need for traditional covalent linkages.
• Providing flexibility, as the structure can adapt to changes in environmental conditions.
• Helping to stabilize the molecular arrangement, which is pivotal for maintaining its polymeric form.

Overall, intermolecular connections like those in boric acid are fundamental in understanding the behavior and properties of materials that rely on hydrogen-bond-induced polymer-like structures.