Question

You have three covalent compounds with three very different boiling points. All of the compounds have similar molar mass and relative shape. Explain how these three compounds could have very different boiling points.

Short answer

The molecules have different intermolecular forces, which lead to different boiling points. The molecules with more or higher intermolecular forces have higher boiling points because they take more energy (here, energy is heat) to break the hydrogen bonds.

Step-by-step solution

Intermolecular forces

The forces of attraction that are present in between the molecules of matter are called intermolecular forces. These forces can influence the physical properties like melting point, boiling point, vapor pressure, etc. of the matter.

The boiling point of a liquid

The boiling point of a liquid is the equilibrium temperature at which a liquid changes from its liquid state to its vapor state. The vapor pressure of the liquid is equal to the applied pressure at this moment.

Relation between intermolecular forces and boiling point:

The greater the intermolecular interactions between liquid particles, the more difficult it is for them to escape into the vapor phase, requiring more energy to convert it from liquid to vapor phase and thus higher its boiling point.

The molecules have different intermolecular forces, which lead to different boiling points though they have similar molar mass and relative shape. The molecules with more or higher intermolecular forces have higher boiling points because they take more energy (here, energy is heat) to break the hydrogen bonds.