Question

Which of the following does not change as a consequence of hydrogen bonding in a compound? (1) colour (2) boiling point (3) density (4) freezing point

Short answer

Colour

Step-by-step solution

Identify Properties Affected by Hydrogen Bonding

Hydrogen bonding significantly affects properties like boiling point, freezing point, and density due to the strong intermolecular forces it creates.

Analyze Each Option

Consider each property listed:1. Colour: Hydrogen bonding usually does not affect the colour of a compound.2. Boiling Point: Hydrogen bonding increases the boiling point.3. Density: Hydrogen bonding can affect the density of a substance by changing how molecules stack together.4. Freezing Point: Hydrogen bonding can raise or lower the freezing point depending on the compound.

Identify the Correct Answer

From the analysis, the property that does not change significantly due to hydrogen bonding is the colour of the compound.

Key concepts

Boiling Point

Boiling point is the temperature at which a substance changes from liquid to gas. Hydrogen bonding significantly influences this.
Strong hydrogen bonds require more energy to break. Thus, substances with hydrogen bonds have higher boiling points compared to those without.
Let's take water as an example. It has hydrogen bonds, which require a lot of heat energy to break, resulting in a high boiling point (100°C).

• Strong hydrogen bonds = Higher boiling point
• Weak or no hydrogen bonds = Lower boiling point

Understanding this is crucial for predicting how a compound will behave when heated.

Density

Density is the mass per unit volume of a substance. Hydrogen bonding affects how molecules are arranged, impacting density.
Molecules with strong hydrogen bonds pack more tightly, often increasing the density.
For example, ice is less dense than liquid water because its hydrogen bonds create an open lattice structure, causing it to float.

• Strong hydrogen bonds = Potential for higher density
• Weaker hydrogen bonds or no hydrogen bonds = Lower density

Knowing how hydrogen bonding affects density helps in understanding the physical states and behaviors of substances.

Freezing Point

Freezing point is the temperature at which a liquid becomes a solid. Hydrogen bonding can greatly affect this property.
Strong hydrogen bonds make it harder for molecules to move, which can lower the freezing point. But in some cases, it can also stabilize a crystal structure, raising the freezing point.
Water is a prime example. Its hydrogen bonding causes it to freeze at 0°C.

• Strong hydrogen bonds = Can either lower or raise the freezing point depending on the specific structure
• Weak or no hydrogen bonds = Generally higher freezing points

Comprehending this concept is vital for predicting how substances behave at lower temperatures.