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  1. Describe the manufacture of sulfuric acid by the Contact process, including essential conditions.

The manufacture of sulfuric acid takes place in a process called the Contact process.

The raw materials required are sulfur, air and water. Sulfur can be obtained from sulfide ores, or extracted as hydrogen sulfide (from petroleum or natural gas) and separated.


  • A spray of molten sulfur is burned in a furnace in a current of dry air. Sulfur dioxide is formed.
    S(l) + O2(g) ————> SO2(g)
  • The sulfur dioxide is cooled and reacted with more air in the converter to form sulfur trioxide. This happens at about 450°C, atmospheric pressure and with the catalyst vanadium(V) oxide present. This catalyst is also known as vanadium (V) pentoxide, and its formula is V2O52SO2(g) +O2(g) ———> 2SO3(g)
  • This sulfur trioxide is absorbed into a 98% solution of sulfuric acid (readily available) in a tower called the absorber.. This forms a thick liquid known as oleum
    SO3(g) +H2SO4(l) ———–> H2S207(l)
  • The oleum is mixed with a little water to make concentrated 98% sulfuric acid:
    H2S207(l) + H2O(l) ————> 2H2SO4(l)

(Memorising tip:  sulfur—–>sulfur dioxide—–>sulfur trioxide—–>oleum—–>sulfuric acid)


  1. Describe the properties of dilute sulfuric acid as a typical acid.

Sulfuric acid has typical acidic properties. It has two hydrogen ions per molecule that can react (H2SO4)

It reacts with metals above hydrogen in the reactivity series to form a salt and hydrogen.

It reacts with metal oxides to form a salt and water

It reacts with metal hydroxides to form a salt and water

It reacts with carbonates to form a salt, water and carbon dioxide

It can form hydrogensulfates by the replacement of one of the hydrogen ions in sulfuric acid:
H2SO4(aq)  +  NaOH(aq) ———-> NaHSO4(aq)  +  H2O(l)
sulfuric acid + sodium hydroxide ——-> sodium hydrogensulfate + water




Notes submitted by Lintha

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4 thoughts on “C12.0 – Sulfur

  1. Great work! But I think you made a typo when writing sulfur trioxide, it should be SO3, you wrote it as SO2. Anyway thanks for the help, this website has really helped!


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