Question

Based on the boiling points of water and methanol, in which would you expect to observe a greater degree of hydrogen bonding? Explain your answer.

Short answer

Water exhibits a greater degree of hydrogen bonding compared to methanol, as indicated by its higher boiling point.

Step-by-step solution

Identify Boiling Points

First, identify the boiling points of water and methanol. The boiling point of water is 100°C, and the boiling point of methanol is 64.7°C.

Understand Hydrogen Bonding

Understand that hydrogen bonding significantly affects the boiling point of a substance. Stronger hydrogen bonds generally result in a higher boiling point.

Compare the Boiling Points

Compare the boiling points of water and methanol. Water has a higher boiling point (100°C) compared to methanol (64.7°C). This suggests that water has stronger intermolecular forces, likely due to hydrogen bonding.

Correlate Boiling Point with Hydrogen Bonding

Conclude that the greater degree of hydrogen bonding corresponds to the higher boiling point. Since water has the higher boiling point, it exhibits a greater degree of hydrogen bonding compared to methanol.

Key concepts

boiling point comparison

Boiling point is the temperature at which a liquid turns into vapor. It helps to give us an idea of the intermolecular forces present in a substance.
For example, the boiling point of water is 100°C, while the boiling point of methanol is 64.7°C.
This difference in boiling points is crucial because it tells us that water has stronger intermolecular forces compared to methanol.
When comparing boiling points, higher values generally indicate stronger intermolecular forces.
In the case of water and methanol, it is clear that water, with its higher boiling point, exhibits stronger intermolecular forces.

intermolecular forces

Intermolecular forces are the forces that hold molecules together. They play a crucial role in determining the physical properties of substances, such as boiling points, melting points, and solubility.
There are several types of intermolecular forces, including:

• Van der Waals forces: Weak forces that arise from temporary dipoles.
• Dipole-dipole interactions: Forces between polar molecules.
• Hydrogen bonds: Strong attractions between hydrogen atoms and electronegative atoms like oxygen, nitrogen, or fluorine.

Hydrogen bonding significantly influences the boiling point of a substance.
Strong hydrogen bonds result in higher boiling points.
Comparing water and methanol, water forms more and stronger hydrogen bonds, leading to its higher boiling point.

water vs methanol

Water (H₂O) and methanol (CH₃OH) both exhibit hydrogen bonding, but the nature and strength of these bonds differ.
In water, each molecule can form four hydrogen bonds—two through its hydrogen atoms and two through its lone pairs of oxygen atoms.
This extensive hydrogen bonding network greatly increases water's boiling point. Methanol molecules, on the other hand, can form hydrogen bonds but not as extensively as water.
Each methanol molecule can form two hydrogen bonds—one through its hydrogen atom and one through its lone pair of oxygen.
Because methanol has fewer opportunities for hydrogen bonding, its boiling point is lower than that of water.
This comparison clearly shows that water, with its higher boiling point, has stronger and more numerous hydrogen bonds than methanol.