Preparation of Sulfuric Acid

Sulphuric acid is an acidic chemical compound with the formula H2SO4. It is widely used in the industries that is why it is called the king of chemicals. Its worldwide production clearly indicates its industrial strength. In the year 2004, its world production was about 180 million tonnes. It is also known as oil of vitriol. It is an odorless, colorless and viscous liquid which is soluble in water. Preparation of sulphuric acid generally involves highly exothermic processes.

Study of the oil of vitriol began in ancient times. It is believed that Muhammad ibn Zakariya al-Razi was the 1st alchemist of Iran who produced sulfuric acid. Then in 17th century German-Dutch Chemist Johann Glauber prepared sulfuric acid by sulfur with potassium nitrate. In 1736, Doctor Joshua Ward used this method for large scale production of sulfuric acid, although it was an expensive method of production. After this many other methods of production of sulfuric acid were also discovered but they were not economically feasible. 

Then in 1831, British vinegar merchant Peregrine Phillips patented the contact process, in which sulfuric acid is produced by using sulfur dioxide and oleum in presence of vanadium pentoxide as catalyst. This method is more economically feasible than available all other methods and produces concentrated sulfuric acid. It is the current method of producing sulfuric acid in large scale and high concentration required for industrial processes. 

Contact Process for Manufacturing of Sulfuric Acid 

Steps involved in contact process of manufacturing of sulfuric acid are listed below–

  • Preparation of sulfur dioxide 

  • Oxidation of sulfur dioxide to prepared sulfur trioxide 

  • Addition reaction of sulfur trioxide and sulfuric acid to give oleum 

  • Dilution of oleum to produce concentrated sulfuric acid 

Preparation of Sulfur Dioxide – In the 1st step sulfur is oxidized or burned to produce sulfur dioxide. Reaction is given below –

S(s) + O2(g) 🡪 SO2(g)

Oxidation of Sulfur Dioxide to Prepare Sulfur Trioxide – Sulfur dioxide is oxidized to sulfur trioxide in presence of vanadium pentoxide as catalyst. It is an exothermic reaction which is reversible in nature. the reaction is given below –

2SO2(g) + O2(g) V2O5 🡪 2SO3(g)

Addition Reaction of Sulfur Trioxide and Sulfuric acid to Give Oleum – Sulfur trioxide is absorbed into ~98% sulfuric acid to form oleum which is also known as fuming sulfuric acid. It is an additional reaction. The reaction is given below –

SO3(g) + H2SO4(l) 🡪 H2S2O7(l)

                                 Oleum 

Dilution of Oleum to Produce Concentrated Sulfuric Acid – Oleum is diluted with water to form concentrated sulfuric acid. The reaction is given below –

H2S2O7(l) + H2O(l) 🡪 2H2SO4(l)

It should be noticed here that we used 1 mole of sulfuric acid as reactant and produced 2moles of sulfuric acid. 

It is an easy to remember explanation of Preparation of Sulfuric acid with emphasis on the currently used preparation method – Contact Process. If you are looking for NCERT Solutions of Chemistry Subject the log on to Vedantu website or Download Vedantu learning app. By doing so you will not only get access to free PDFs of NCERT Solutions of Chemistry but other subjects as well.