Question

The oxidation of $S{O}_2$ by $O_2$ to $S{O}_3$ is an exothermic reaction according to equation $2S{O}_2\left(g\right)+O_2\left(g\right)\rightleftharpoons 2S{O}_3\left(g\right)+\text{Heat}$. The yield of $S{O}_3$ will be maximum if

• A. temperature is increased and pressure is kept constant
• B. temperature is reduced and pressure is increased
• C. both temperature and pressure are increased
• D. both temperature and pressure are reduced

Answer 1

The correct option is B temperature is reduced and pressure is increased

(i) According is Le-chatelier's principle, exothermic reaction is favoured at low temperature.
(ii) According to Le-chatelier's principle, the reaction in which the difference in the total number of gaseous molecules in the product and reactant is leass than zero i.e. n < 0, is favoured at high pressure.
Given $2S{O}_2\left(g\right)+O_2\left(g\right)\rightleftharpoons 2S{O}_3\left(g\right)+\text{Heat}$
$\because$ it is exothermic reaction
$\therefore$ Yield of $S{O}_3$ will be increased at low temperatures.
Also, $n=2-3=-1$ or n < 0
$\therefore$ Yield of $S{O}_3$ will be increased at high pressures.
Lower temperature and higher pressure will give maximum oxidation of sulphur dioxide to sulphur trioxide