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sludger13
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I'd like to know the physical mechanism of oleum "fuming" on its surface. Dissolved SO3 reacts very exothermically with some air humidity. Why does the mist occur instead of dissolving created H2SO4 in the solution?
sludger13 said:Why does the mist occur instead of dissolving created H2SO4 in the solution?
You've pretty much answered your own question here.sludger13 said:SO3 reacts very exothermically with some air humidity
No, that is too simplified.Bystander said:You've pretty much answered your own question here.
Cp(H2SO4, liq) ~ 60 J/molK, and the enthalpy of the reaction between SO3 and water vapor at the surface is around 160 kJ/mol. Fume? You bet you --- that's the old "acid to water, never water to acid" rule from HS chemistry.sludger13 said:Or sulfuric acid with (~300°C, p(atm)) boiling point?
That makes me more sense, thank you.Borek said:My bet is that the concentration (partial pressure) of SO3 above oleum is high enough to start condensation in the presence of water vapor. That will happen above the surface, in the gas phase.
When water putted into acid or conversely acid putted into water, the liquid may spit around due to gas expansion, as I see. Also that is different physical process than oleum fuming.Bystander said:Fume? You bet you --- that's the old "acid to water, never water to acid" rule from HS chemistry.
Oleum fuming is a chemical process in which liquid oleum (a mixture of sulfur trioxide and sulfuric acid) is exposed to air, causing it to release fumes. This process is often used in industrial settings to produce strong acids.
Oleum fuming works through a physical mechanism known as hydrolysis. When exposed to air, the sulfur trioxide in oleum reacts with water vapor to form sulfuric acid, which then releases fumes. This process can also occur with other compounds, such as nitric acid, but oleum is known for its particularly strong fuming properties.
Oleum fuming has several industrial uses, such as in the production of nitric acid, gasoline additives, and detergents. It is also commonly used in laboratory settings for chemical reactions and as a dehydrating agent.
Yes, oleum fuming can be dangerous if not handled properly. The fumes released can cause irritation to the eyes, nose, and throat, and can also be corrosive to skin. It is important to use proper safety precautions, such as wearing protective gear and working in a well-ventilated area, when handling oleum.
Oleum fuming can be investigated through various techniques, such as infrared spectroscopy and gas chromatography, to analyze the chemical composition of the fumes. Additionally, experiments can be conducted to observe the physical mechanism of hydrolysis and measure the amount of fumes released under different conditions.