Contact process for preparation of h2so4

Contact process for sulphuric acid: The manufacturing process is completed in the following steps:
Step 1: Burning of either sulphur or iron pyrites in the air to give SO₂
{tex}{S\; + {O_2} \to \;S{O_2}}{/tex}

{tex}{Fe{S_2}\; + 11{O_2}\; \to 2F{e_2}{O_3}\; + \;8S{O_2}}{/tex}
Step 2: Catalytic Conversion of SO₂ to SO₃ by reacting it with oxygen in presence of V₂O₅ as a catalyst.
{tex}2S{O_2} + {\text{ }}{O_2}\;\xrightarrow{{{V_2}{O_5}}}2S{O_3}{/tex} , {tex}\triangle H=\;-196.6\;KJ/mol{/tex}. 
Step 3: Absorption of {tex}S{O_3}{/tex} in {tex}{H_2}S{O_4}{/tex} to give of oleum {tex}\left( {{H_2}{S_2}{O_7}} \right){/tex}
{tex}S{O_3} + {\text{ }}{H_2}S{O_4}\; \to {H_2}{S_2}{O_7}\left( {oleum} \right){/tex}
Step 4: Dilution of oleum with water to get off the H₂SO₄ desired concentration
{tex}{H_2}{S_2}{O_7} + {H_2}O \to 2{H_2}S{O_4}{/tex}