International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Why does nitrogen gas, N₂, exist as a gas at room temperature?

1. It has a high melting point

2. It has a simple molecular structure with strong intermolecular forces

3. It has a simple molecular structure with weak intermolecular forces

4. It has a complex molecular structure

The correct answer is: It has a simple molecular structure with weak intermolecular forces

Nitrogen gas exists as a gas at room temperature primarily due to its simple molecular structure combined with weak intermolecular forces known as van der Waals forces. Nitrogen molecules consist of two nitrogen atoms bonded together (N≡N), forming a diatomic molecule. The interactions between these nitrogen molecules are not strong because the only forces acting between them are the relatively weak van der Waals forces. These weak forces allow nitrogen molecules to move freely past one another, resulting in a gaseous state. In contrast, substances with strong intermolecular forces generally exist as solids or liquids at room temperature, as these forces hold the molecules closer together, restricting their movement. Therefore, the weak intermolecular forces in nitrogen gas facilitate its existence as a gas at room temperature.