Final answer:
To shift the equilibrium of the system N₂(g) + 3H₂(g) ⇌ 2NH₃(g) to the left, adding more NH₃(g) would be the effective stress because it increases the concentration of products, leading the equilibrium to favor the reverse reaction.
Step-by-step explanation:
The question asks which stress will shift the following equilibrium system to the left: N₂(g) + 3H₂(g) ⇌ 2NH₃(g). Applying Le Chatelier's principle, we can analyze how different changes will affect the equilibrium.
- Adding more N₂(g) will actually shift the equilibrium to the right because it increases the reactant concentration, favoring the formation of more NH₃ to re-establish equilibrium.
- Adding more NH₃(g) shifts the equilibrium to the left, as it increases the product concentration and the system will favor the reverse reaction to reduce this concentration.
- Increasing the pressure of the system, either by reducing the volume of the container or by adding more of one of the components, will shift the equilibrium towards the side with fewer gas molecules. Since the formation of NH₃ results in fewer gas molecules (2 molecules from 4), increasing pressure shifts the equilibrium to the right.
- Reducing the volume of the container similarly increases the pressure, favoring the side with fewer moles of gases, which is the product side in this case.
Therefore, to shift the equilibrium to the left, adding more NH₃(g) would be the effective stress.