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Pure sulfuric acid does not occur naturally due to its strong affinity to water vapor; it is hygroscopic and readily absorbs water vapor from the air. [7] Concentrated sulfuric acid is a strong oxidant with powerful dehydrating properties, making it highly corrosive towards other materials, from rocks to metals.
The first and faster [citation needed] process is the removal of hydrogen and oxygen as units of water by the concentrated sulfuric acid. This occurs because hydration of concentrated sulfuric acid is strongly thermodynamically favorable, with a standard enthalpy of reaction of −880 kJ/mol.
Alkenes can be made from alcohols by dehydration. This conversion, among others, is used in converting biomass to liquid fuels. [2] The conversion of ethanol to ethylene is a fundamental example: [3] [4] CH 3 CH 2 OH → H 2 C=CH 2 + H 2 O. The reaction is accelerated by acid catalysts such as sulfuric acid and certain zeolites.
Using a dehydrating agent: sulfuric acid not only catalyzes the reaction but sequesters water (a reaction product). Other drying agents such as molecular sieves are also effective. Removal of water by physical means such as distillation as a low-boiling azeotrope with toluene, in conjunction with a Dean-Stark apparatus.
It is also prepared by the dehydration of sugar in the presence of concentrated sulfuric acid. Since sulfuric acid is a dehydrating agent, it absorbs water from the sugar and leaves behind black residue of carbon. It is the purest form of amorphous carbon. [citation needed]
The carbon snake is a demonstration of the dehydration reaction of sugar by concentrated sulfuric acid. With concentrated sulfuric acid, granulated table sugar performs a degradation reaction which changes its form to a black solid-liquid mixture. [1] The carbon snake experiment can sometimes be misidentified as the black snake, "sugar snake ...
In the laboratory, furfural can be synthesized from plant material by heating with sulfuric acid [21] or other acids. [ 22 ] [ 20 ] With the purpose to avoid toxic effluents, an effort to substitute sulfuric acid with easily separable and reusable solid acid catalysts has been studied around the world. [ 23 ]
sulfuric acid (98.3%) / water, boils at 338 °C The adjacent diagram shows a negative azeotrope of ideal constituents, X and Y. Again the bottom trace illustrates the boiling temperature at various compositions, and again, below the bottom trace the mixture must be entirely liquid phase.
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