For the reaction 2SO2(g) + 02(g) = 2S03(g) + Heat, the yield of S03 will be maximum if

The reaction 2SO2(g) + O2(g) ⇌ 2SO3(g) + Heat is an exothermic process, as indicated by the release of heat [c1][c4]. According to Le Chatelier's principle, a system at equilibrium responds to stress by shifting to counteract the change [t5]. Since the forward reaction is exothermic, decreasing the temperature shifts the equilibrium to the right to produce more heat, thereby increasing the yield of SO3 [t2][t3]. Regarding pressure, the reactant side has 3 moles of gas (2 SO2 + 1 O2) while the product side has 2 moles (2 SO3). Increasing the pressure favors the side with fewer gaseous moles to reduce the stress [t1][t3]. Therefore, the yield of SO3 is maximized under conditions of decreased temperature and increased pressure [t2].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > QUESTIONS > p. 7
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > What you have learnt > p. 14