What is the reason for considering N2 has a boiling point lower than O2,because of its low molecular mass.
Just curious about that old reason...
One mole N2 is 28 g. One mol O2 is 32 g. It takes less energy to move a 28 g mass than a 32 g mass. 1
Thank you!
The reason for considering N2 (nitrogen) to have a lower boiling point than O2 (oxygen) is indeed related to its low molecular mass. To understand this, let's break it down step by step:
1. Molecular Mass: The molecular mass of a molecule is the sum of the atomic masses of all the atoms in the molecule. In the case of nitrogen (N2) and oxygen (O2), nitrogen has a lower molecular mass than oxygen. The molecular mass of nitrogen is approximately 28 atomic mass units (amu), while oxygen has a molecular mass of about 32 amu.
2. Intermolecular Forces: Boiling is the process in which a substance changes from its liquid state to its gaseous state, and it occurs when the vapor pressure of the liquid equals the atmospheric pressure. The key factor influencing the boiling point of a substance is the strength of the intermolecular forces between its molecules. Intermolecular forces are attractive forces between molecules.
3. London Dispersion Forces: In the case of N2 and O2, the dominant intermolecular forces are London dispersion forces, also known as van der Waals forces. These forces arise due to temporary fluctuations in electron distribution, which cause temporary dipoles in the molecules. These temporary dipoles induce temporary dipoles in neighboring molecules, leading to attractive forces.
4. Relation to Molecular Mass: London dispersion forces depend on the ease with which temporary dipoles can form and induce dipoles in neighboring molecules. This ease is influenced by the size, shape, and molecular mass of the molecules. Generally, larger molecules with higher molecular masses have stronger London dispersion forces because the electrons are more spread out, leading to larger temporary dipoles and stronger attractions.
5. Boiling Point: Since nitrogen has a lower molecular mass than oxygen, the nitrogen molecules are smaller and have fewer electrons, resulting in weaker London dispersion forces compared to oxygen. Weaker intermolecular forces make it easier for nitrogen molecules to overcome these forces and enter the gaseous state, thus having a lower boiling point compared to oxygen.
It's important to note that the boiling points of gases are also influenced by other factors, such as the presence of other intermolecular forces like dipole-dipole interactions or hydrogen bonding. However, in the case of nitrogen and oxygen, the main factor is the difference in their molecular masses and the resulting difference in the strength of their London dispersion forces.