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Miffymycat
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Ethanol has a higher ΔHvap than water (43.5 vs 41.3 kJ/mol). But water has a higher boiling point (373 vs 352K). How do we explain this?!
Miffymycat said:Ethanol has a higher ΔHvap than water (43.5 vs 41.3 kJ/mol). But water has a higher boiling point (373 vs 352K). How do we explain this?!
Miffymycat said:Thanks guys
Right. But even under a vacuum, liquids can still have a highish boiling point. I still find it hard to visualise the difference between the kinetic energy to overcome the IMF's by heating to the boiling point - at which point the forces between them are sufficiently low to enable the substance to overcome any external pressure and leave the liquid and the extra energy required to change the state ie enthalpy of vapourisation! What is this extra for? There no forces to overcome now!
Thank for your patience!
The enthalpy of vaporization is the amount of energy required to change a substance from liquid to gas at its boiling point, while the boiling point is the temperature at which a substance changes from liquid to gas at a given pressure.
The strength of intermolecular forces, the size of the molecules, and the temperature and pressure of the surrounding environment all affect the enthalpy of vaporization.
The enthalpy of vaporization is important because it is a measure of the energy required to transform a substance from liquid to gas. This information is useful in various industries, such as in the design of refrigeration systems and in the production of fuels.
The enthalpy of vaporization varies among different substances due to differences in intermolecular forces and molecular size. For example, substances with stronger intermolecular forces and larger molecules will have a higher enthalpy of vaporization.
No, the enthalpy of vaporization cannot be negative. It is always a positive value because energy must be added to a substance in order for it to change from liquid to gas.