The key step in the manufacture of H2SO4 is

The key step in the manufacture of H2SO4 is      2SO2(g)+O2(g)→V2O52SO3(g);ΔrH∘=−196.6kJ mol−1This reaction is endothermic, reversible and the forward reaction leads to a decrease in volume. Thus, low temperature and high pressure are the favourable conditions for maximum yield. But the reaction should not be very low other wise rate of reaction will become slow.