What is the boiling point of h2?
The Correct Answer and Explanation is:
The boiling point of hydrogen (H₂) is −252.87°C or 20.28 K. This low boiling point is due to the molecular properties of hydrogen.
Explanation:
Hydrogen is a diatomic molecule composed of two hydrogen atoms (H₂), and it exists as a gas at standard temperature and pressure (STP). The boiling point of a substance is the temperature at which its vapor pressure equals the atmospheric pressure, causing the liquid to transition into a gas. In the case of hydrogen, its boiling point is extremely low compared to most substances, which can be attributed to the following factors:
- Weak Intermolecular Forces (Van der Waals forces):
Hydrogen molecules are held together by very weak intermolecular forces, specifically London dispersion forces (a type of Van der Waals force). These forces arise from temporary dipoles created by the movement of electrons within the molecule. Because these forces are weak, it takes very little energy to overcome them and turn hydrogen from a liquid into a gas, resulting in a low boiling point. - Small Molecular Size:
Hydrogen is the smallest molecule in terms of atomic size, with only a single proton and a single electron per atom. The small size of hydrogen molecules contributes to the weak van der Waals forces between them. Larger molecules, with more electrons and greater mass, experience stronger intermolecular forces, which require more energy (and a higher temperature) to break. - Low Molecular Weight:
Hydrogen has an atomic weight of approximately 1 g/mol, which is much smaller than the molecular weights of many other gases. Gases with smaller molecular weights generally have lower boiling points because their molecules are more easily separated by the energy provided in the form of heat. - Boiling Point in Relation to Other Gases:
To put it in perspective, hydrogen’s boiling point of −252.87°C is much lower than that of oxygen (−183°C), nitrogen (−195.8°C), or even helium (−268.93°C). This is due to its small size and weak intermolecular forces.
Overall, hydrogen’s low boiling point reflects its molecular characteristics, particularly its small size and weak intermolecular attractions, making it one of the most volatile and lightest gases in the periodic table.