Question

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

Short answer

The polymeric nature of boric acid is due to the presence of hydrogen bonds.

Step-by-step solution

Understand the nature of boric acid

Boric acid is a weak acid with the chemical formula \( \text{H}_3\text{BO}_3 \). It is not a typical proton donor and acts as a Lewis acid by accepting hydroxide ions \( \text{OH}^- \). The acid itself is not primarily responsible for polymerization.

Examine the potential for hydrogen bonding

Boric acid consists of a planar trigonal structure, where each boron atom is bonded to three hydroxyl groups. These groups have hydrogen atoms that can form hydrogen bonds with adjacent oxygen atoms from other boric acid molecules, leading to the formation of chains or layers of molecules.

Consider boric acid's basicity

Boric acid is a monobasic acid, meaning it can release only one hydrogen ion per molecule. This property is more related to its behavior in solution rather than its structure. Monobasic nature itself doesn't cause polymerization.

Analyze the geometric structure of boric acid

The planar geometry of boric acid facilitates close packing and the formation of hydrogen bonds between molecules. However, the geometry itself doesn't directly cause polymerization, but it allows for extensive hydrogen bonding.

Conclusion on polymerization

The polymeric nature of boric acid is primarily due to the extensive hydrogen bonding that occurs between the OH groups of adjacent boric acid molecules.

Key concepts

Hydrogen Bonding

In the world of chemistry, hydrogen bonding plays a very significant role, especially in the case of boric acid polymerization. Hydrogen bonds are a type of weak chemical bond that occurs when a hydrogen atom covalently bonded to a more electronegative atom, like oxygen, is also attracted to another electronegative atom. This is the case in boric acid (\( \text{H}_3\text{BO}_3 \)), where each boron atom is attached to three OH groups. The hydrogen atoms in these OH groups can form hydrogen bonds with oxygen atoms in nearby boric acid molecules, resulting in extended chains or layers of boric acid molecules tightly bonded together.

Notably, these hydrogen bonds, although weak compared to covalent bonds, are numerous and collectively strong enough to give rise to the polymeric structure observed in boric acid. Thus, the prevailing structure and behavior of boric acid in solution largely result from these repeated intermolecular interactions.

• Acts between hydrogen and electronegative atoms
• Collectively strong, though individually weak
• Responsible for polymeric formations in boric acid

Lewis Acid

Boric acid is an interesting example of a Lewis acid, which is a concept that diverges slightly from the traditional view of what an acid is. Instead of donating protons (H+ ions), a Lewis acid accepts electron pairs. In the case of boric acid, it accepts a hydroxide ion (\( \text{OH}^- \)) from water, forming the complex \( \text{B(OH)}^-_4 \). This occurs because the boron atom in boric acid has an incomplete octet, meaning it is electron-deficient. Hence, it pursues electron pairs to complete its valence shell.

Being a Lewis acid also provides boric acid with unique properties in chemical reactions and contributes to its behavior in forming hydrogen bonds, which further encourages its polymeric structure in solution.

• Accepts electron pairs
• Boron has an incomplete octet
• Contributes to boric acid's polymeric nature

Monobasic Acid

Boric acid is known as a monobasic acid, indicating that it can only release one hydrogen ion (\( ext{H}^+ \)) per molecule into solution. However, this is somewhat misleading when considering its polymerization properties. Unlike classical acids which release hydrogen ions directly, boric acid behaves differently in aqueous solutions.

Its monobasicity signifies the release capability of only one ion, but this is related more to reaction behavior rather than contributing directly to polymeric properties. Instead, the structural formation—polymerization—is mainly due to hydrogen bonding rather than the monobasic nature. Thus, while its basic nature leads to certain solution behaviors, it's not a driving factor for polymerization.

• Can release one \( ext{H}^+ \) only
• More related to acid behavior in reactions
• Doesn't directly cause polymerization

Planar Geometry

Boric acid features a distinctive planar geometry, with each boron atom forming three coordinate covalent bonds with hydroxyl groups. This planar arrangement allows boric acid molecules to pack closely together in a layer-like arrangement.

This geometry is quite significant for enabling extensive hydrogen bonding. While the geometry itself does not directly cause polymerization, it positions the molecules in such a way that maximizes potential hydrogen bonding interactions. In essence, boric acid's planar geometry sets the stage for the polymerisation processes driven by hydrogen bonding.

• Allows close packing of molecules
• Enables hydrogen bond formation
• Facilitates extended molecular interactions