Chemistry - Complete P-block Question with Solution | TestHub

The reaction is

$2{\mathrm{SO}}_2(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 2{\mathrm{SO}}_3(\mathrm{g})$,

which is exothermic ($\Delta H<0$) and involves a decrease in the number of moles of gas (3 moles reactants to 2 moles products). According to Le Chatelier's principle, low temperature favors exothermic reactions, and high pressure favors the side with fewer moles of gas.

Therefore, low temperature and high pressure are most favorable.