Sulfur trioxide, reaction with water Sulfuric acid

Sulfuric acid (H2S04), the most widely produced chemical in the world, is made by a two-step oxidation of sulfur to sulfur trioxide, SO3, followed by reaction with water. Calculate AH°f for SO3 (in kilojoules per mole), given the following data ... 

The properties of sulfur trioxide may be in large part explained as resulting from the instability of the sulfur-oxygen double bond. Thus by reaction with water the double bond can be replaced by two single bonds, in sulfuric acid ... 

Chlorosulfonyl isocyanate (LXXXI) is formed in the reaction of eyanogen chloride with sulfur trioxide in a 1 1 molar ratio (57, 58), and this is saponified by water vapor (59) or formic acid (2) to amidosulfonic acid chloride (LXXXIX), H2NS02C1. It is colorless and crystalline and melts at 40-41°. The reaction with water is explosive, amidosulfonic acid and HC1 being formed. 

The equilibrium constant for this reaction is 1.7 X 10 , which indicates that for all practical purposes the reaction should go almost completely to products. Yet when sulfur is burned in air or oxygen, it forms predominantly SO2 and very little SO3. Oxidation of SO2 to SO3 is simply too slow to give a significant amount of product. However, the rate of the reaction is appreciable in the presence of a platinum or divanadium pentoxide catalyst. The oxidation of SO2 in the presence of a catalyst is the main step in the contact process for the industrial production of sulfuric acid, H2SO4. Sulfur trioxide reacts with water to form sulfuric acid. (In the industrial process, SO3 is dissolved in concentrated H2SO4, which is then diluted.) ... 

Sulfuric Acid. Generally, sulfuric acid of 93—99% is used. The sulfuric values may be fed to the plant as H2SO4, oleum (20% SO ), or even SO (see Sulfuric acid and sulfur trioxide). Commonly, both H2SO4 and oleum are used. The spHt between the two is determined by water balance. AH water entering the process or produced by side reactions reacts with the SO component of the oleum ... 

Sulfamic acid [5329-14-6] (amidosulfuric acid), HSO2NH2, molecular weight 97.09, is a monobasic, inorganic, dry acid and the monoamide of sulfuric acid. Sulfamic acid is produced and sold in the form of water-soluble crystals. This acid was known and prepared in laboratories for nearly a hundred years before it became a commercially available product. The first preparation of this acid occurred around 1836 (1). Later work resulted in identification and preparation of sulfamic acid in its pure form (2). In 1936, a practical process which became the basis for commercial preparation was developed (3,4). This process, involving the reaction of urea with sulfur trioxide and sulfuric acid, continues to be the main method for production of sulfamic acid. 

The chemical reactions appear simple. They begin with pure sulfur (which occurs in natural deposits in the elemental state). First, sulfur is burned to give gaseous sulfur dioxide, S02. Next, the S02 is further oxidized, catalytically, to sulfur trioxide, SO ,. Finally, addition of water forms sulfuric acid. The reactions are ... 

In the most common process for making sulfuric acid, sulfur is burned at a very high temperature in dry air to make sulfur dioxide, which is then reacted with more oxygen over a catalyst to make sulfur trioxide. Reaction of sulfur trioxide with water produces sulfuric acid. 

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