Question

The boiling point of water is exceptionally high because: (a) There is covalent bond between \(\mathrm{H}\) and \(\mathrm{O}\) (b) Water molecule is not linear (c) Water molecule is linear (d) Water molecules associate due to hydrogen bonding

Short answer

Water's high boiling point is due to hydrogen bonding between molecules.

Step-by-step solution

Understanding the Question

We are asked which reason explains why the boiling point of water is exceptionally high. This involves understanding the structural and interaction properties of water molecules.

Analyzing Covalent Bonds

Covalent bonds between \( ext{H}\) and \( ext{O}\) atoms are strong bonds that hold individual water molecules together. These are intramolecular forces. However, they do not explain high boiling point related to intermolecular forces.

Assessing Molecular Shape

Consider options about structure: water is not linear, its bent shape isn't directly related to high boiling point, but impacts polarity. Neither statement (b) nor (c) directly explains the high boiling point.

Investigating Hydrogen Bonding

Hydrogen bonding is an intermolecular force occurring between water molecules due to its polar nature. This strong intermolecular force results in higher energy required to break these bonds, leading to a high boiling point.

Choosing the Best Explanation

Of the options given, the high boiling point of water is best explained by the association of water molecules through hydrogen bonding, which is represented by option (d).

Key concepts

Boiling Point of Water

The boiling point of water is an interesting topic because it is remarkably high for such a small molecule. To put it into perspective, water boils at 100°C (212°F), which is significantly higher than other molecules of similar size and weight. This is largely because of the unique interactions that occur between water molecules.
The high boiling point is due to the energy required to separate water molecules. When water is heated, the molecules move faster and collide, eventually overcoming the attractive forces that hold them together. The key player here is the hydrogen bond. These are strong intermolecular forces which require more energy to break, resulting in a higher temperature needed to reach the boiling point.

• Water boils at 100°C because of strong hydrogen bonds.
• More energy is needed to break these bonds when boiling.
• This results in a high boiling point compared to other similar molecules.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion which act between neighboring particles, including atoms, molecules, or ions. In the case of water, the most significant intermolecular force is hydrogen bonding. It's important to distinguish these from intramolecular forces, which occur within a molecule.
Hydrogen bonds are a type of dipole-dipole interaction specifically involving a hydrogen atom bonded to a highly electronegative atom, such as oxygen in water (H₂O). Because of this bonding, each water molecule can form multiple hydrogen bonds with surrounding water molecules. This network of hydrogen bonds is what gives water many of its unique properties, including its high boiling point.

• Hydrogen bonds are strong intermolecular forces.
• They result in higher boiling points.
• These bonds contribute to water's unique properties.

Molecular Polarity in Water

Water's molecular polarity is a crucial factor in the formation of hydrogen bonds. A water molecule consists of two hydrogen atoms covalently bonded to an oxygen atom, forming a bent shape. This bent shape creates a distribution of electrical charge, making water a polar molecule.
The oxygen atom is more electronegative than hydrogen, so it pulls the shared electrons closer to itself, creating a partial negative charge at the oxygen end, with a partial positive charge at the hydrogen end. This charge separation within the molecule allows water molecules to interact strongly with each other through hydrogen bonds.

• Water is a polar molecule due to its bent shape and charge distribution.
• This polarity allows for the formation of hydrogen bonds.
• Polarity leads to unique properties such as high boiling point and surface tension.