Practical pressure utilized in contact process

• Oxidation of sulfur dioxide to sulfur trioxide is a reversible reaction.
• At normal conditions, the equilibrium is far to the left and the amount of sulfur trioxide formed is very less. To improve the formation of sulfur trioxide, the reaction is carried out at around 450-degree celsius(720 kelvin)(high temperature)  and 2 atm pressure (low pressure) in presence of  Pt, which acts as a catalyst.

$2{\mathrm{SO}}_2\left(\mathrm{ }\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{ }\mathrm{g}\right)\frac{{\mathrm{V}}_2{\mathrm{O}}_5\text{ or Pt }}{\overline{450°\mathrm{C},2\mathrm{ }\mathrm{a}\mathrm{t}\mathrm{m}.}}2{\mathrm{SO}}_3\left(\mathrm{ }\mathrm{g}\right);\Delta \mathrm{H}=-197{\mathrm{k}\mathrm{J}\mathrm{.}\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}$