In the reaction, 2SO2 (g) + O2 ⇌ 2SO3 (g) ∆H= -X cal most favorable conditions of temperature and pressure for a greater yield of SO3 are:

Explanation

The correct answer is Option D: Low temperature and high pressure. According to Le Chatelier's principle, increasing the pressure will shift the equilibrium towards the side with fewer gas moles, which is the product side (2SO3), resulting in a higher yield of SO3. Additionally, since the reaction is exothermic (∆H = -X cal), lowering the temperature will also favor the forward reaction, further increasing the yield of SO3. The combination of low temperature and high pressure is thus the most favorable for maximizing the production of SO3. Other options either incorrectly prioritize temperature and pressure conditions that do not favor the formation of SO3 or apply an incorrect understanding of Le Chatelier's principle.