Chemistry
Chemistry
Problem
The synthesis of ammonia, 3 H2(g) + N2(g) ⇌ 2 NH3(g), ΔH° = –92 kJ mol⁻¹, is at equilibrium at 400 K when the temperature is altered as described below; all other conditions remain constant. (i) Temperature is raised by 30 K. (ii) Temperature is raised by 10 K. (iii) Temperature is lowered by 15 K. Rank the trials from greatest to least in terms of the extent of the shift toward decomposition of NH3 that will occur as new equilibrium is established.Intuitive explanation
This problem tests Le Chatelier's principle applied to temperature changes in an exothermic reaction. Since ammonia synthesis releases heat (ΔH° is negative), raising temperature favors the reverse reaction (decomposition), while lowering it favors the forward reaction. The key insight is that a larger temperature increase causes a stronger shift toward decomposition—the equilibrium moves further left to counteract the added heat. Rank by how much each temperature change pushes the system backward.
Intuitive explanation
This problem tests Le Chatelier's principle applied to temperature changes in an exothermic reaction. Since ammonia synthesis releases heat (ΔH° is negative), raising temperature favors the reverse reaction (decomposition), while lowering it favors the forward reaction. The key insight is that a larger temperature increase causes a stronger shift toward decomposition—the equilibrium moves further left to counteract the added heat. Rank by how much each temperature change pushes the system backward.