[Thinking] Concentrated sulfuric acid also contains H2O. Why doesn't concentrated sulfuric acid remove the water in concentrated sulfuric acid?
2026-03-27 10:24:45
Scientific Grain Officer Answers:Concentrated sulfuric acid really removes water from sulfuric acid, and free sulfur trioxide (SO) can be formed in 98% concentrated sulfuric acid.3The reaction mechanism is as follows:
1. In the absence of almost no water, one molecule of sulfuric acid undergoes a proton transfer reaction with another molecule of sulfuric acid, also known as the autodual ionization reaction of sulfuric acid, resulting in the formation of hydrogen sulfate ion HSO4- and protonated sulfuric acid molecule H3SO4+：
2. Protonated sulfuric acid molecule H3SO4+ decomposed into SO3And hydrated hydrogen ion H3O+：
The total response can be written as:
It is equivalent to the capture of water from another molecule of sulfuric acid and the formation of hydrated hydrogen ions H.3O +, another molecule of sulfuric acid is dehydrated to SO3Therefore, 98% concentrated sulfuric acid contains free SO.3Yes, it is more pronounced when the temperature increases.SO3It can attack the benzene ring and undergo a sulfonation reaction, eventually generating benzene sulfonic acid (C6H5—SO3H), learned in high school organic chemistry. In the sulfonation reaction of benzene sulfonated by concentrated sulfuric acid, the real main sulfonating agent includes sulfur trioxide SO3Protonated sulfuric acid molecule H3SO4+, etc., SO in concentrated sulfuric acid3And H3SO4+ is generated by the above reaction.
