The Chemistry of Sulfuric Acid
The Industrial Chemical Produced in the Largest Volume in the World
Oct 5, 2007
One of the chemical industry's most important products, this acid is also present in acid rain and makes your eyes water when chopping onions. This article will describe the important industrial manufacturing processes and some of its many uses.
Sulfur Dioxide
Acid rain has been a problem for developed countries ever since the Industrial Revolution. One of the main causes of acid rain are the oxides of sulfur, which are produced when many metal ores are smelted. This is because the ores contain compounds of the metal with sulfur, called sulfides. When the metal is extracted sulfur dioxide and trioxide are given off as gases. These gases dissolve in water in the clouds, forming a solution of sulfuric acid. This acid rain causes many problems, from killing trees and fish to dissolving historic buildings.
Contact Process
This process, which causes so many problems for the environment, is similar to the industrial production of sulfuric acid, a chemical which is so foundational to industry that its use has been used as a measure of a country's level of industrialisation. When sulfur or a sulfide are strongly heated in air, sulfur dioxide gas is produced. This oxide must be converted to sulfur trioxide in order to produce sulfuric acid. The process by which this is done is called the Contact process and is done over a vanadium(V) oxide catalyst at 450 degrees Centigrade. The sulfur dioxide is then absorbed in sulfuric acid to form a very corrosive chemical called oleum which is then diluted with water to form sulfuric acid.
Properties
When concentrated sulfuric acid is a dense liquid which is extremely corrosive. It reacts very vigorously with water, producing a lot of heat, so if water is added to it it boils instantly, causing concentrated acid to be sprayed into the air. To dilute it the acid must always be added slowly to water with cooling. It reacts with metals and alkalis like other mineral acids. It is also an oxidising agent and a dehydrating agent. An interesting reaction is seen by adding concentrated sulfuric acid to granulated sugar. A black solid is produced as the hydrogen and oxygen atoms are removed from the sugar leaving behind carbon.
Uses
A major use of sulfuric acid in industry is in the manufacture of fertilizers. It is reacted with phosphate rocks to produce phosphoric acid, from which phosphate fertilizers are made. It is also reacted with ammonia from the decomposition of coal to produce ammonium sulphate which is also an important fertilizer. It is also used in the manufacture of paints, plastics and detergents. Of course it is also the acid in the lead-acid batteries we use in our cars.
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