Different compounds have various boiling points. It can be a negative temperature or very high temperature. This depends on several factors of compounds.
Explain, why oxygen has a boiling point of -1830C, hydrogen bromide (-660C) and ethanol (C2H5OH) 780C? Please explain this behavior.
asked by: Sorcha Eckhardt, 2019-06-02
Oxygen (O2), hydrogen bromide (HBr) and ethanol (C2H5OH) have boiling points of -1830C, -660C and 78.370C respectively.
From these three compounds, ethanol has the highest boiling point. Now we try to understand what are the reasons for those different boling points.
Boiling point depends on following factors.
The stronger the intermolecular forces, the higher the boiling point.
The higher the molecular mass, the higher the boiling point.
Van der Waals force < Dipole-Dipole forces < Hydrogen bonds
When intermolecular forces increases, the ability of increasing boiling point is high.
Due to weakest intermolecular forces and lowest molecular weight, O2 has the lowest boiling point.
Hydrogen bonds effect is much stronger than molecular weight. Therefore, C2H5OH has the highest boiling point.
Both ethanol and water molcules have the capability of form hydrogen bonds. So, in aqueous ethanol solution, there are hydrogen bonds between ethanol and water molecules. If we simplify this furthermore, we can say, there are hydrogen bonds between ethanol molecues and water molecules.
Usually, we say, when molecular weight increases, boiling point increases. As an example, boiling point of ethanol is higher than methanol.
But, this is not true at sometimes. As an example, boiling point of water is much higher than H2S. This is caused due to strength of intermolecular forces.
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