N₂(g) + 3H₂(g) ⇌ 2 NH₃ (g); ΔHrxn = -92.4 kJ, meaning the reaction is exothermic. Given the aforementioned details, how will the equilibrium of the system be affected if (a) more N₂ will be added, (b) decrease in temperature, and (c) increase in pressure?
A. Increase in pressure will favor the forward reaction
B. Increase in pressure will favor the reverse reaction
C. Adding more N₂ will favor the reverse reaction
D. Decrease in temperature will favor the forward reaction
E. Decrease in temperature will favor the reverse reaction
F. Adding more N₂ will favor the forward reaction
To determine how the equilibrium of the system will be affected by different changes, we can apply Le Chatelier's principle. This principle states that when a system at equilibrium is subjected to a change, it will adjust itself in a way that minimizes the effect of that change and restores equilibrium.
(a) If more N₂ is added to the system, it will increase the concentration of N₂. According to Le Chatelier's principle, the system will try to counteract this change and restore equilibrium. As a result, the forward reaction will be favored to consume the excess N₂. Therefore, adding more N₂ will actually favor the forward reaction, leading to more NH₃ being produced.
So, option (F) is correct: Adding more N₂ will favor the forward reaction.
(b) A decrease in temperature will shift the equilibrium in the direction that produces heat. Since the reaction is exothermic (ΔHrxn = -92.4 kJ), the forward reaction releases heat. By decreasing the temperature, the system will try to counteract this change and generate more heat. Consequently, the equilibrium will shift to favor the forward reaction, which produces heat.
Therefore, option (D) is correct: Decrease in temperature will favor the forward reaction.
(c) Increasing the pressure will favor the side of the reaction with fewer moles of gas. In this case, there are fewer moles of gas on the right side (2 moles of NH₃) compared to the left side (4 moles of N₂ + 6 moles of H₂). According to Le Chatelier's principle, the system will shift the equilibrium to the side with fewer moles of gas to counteract the increase in pressure. Therefore, increasing the pressure will favor the forward reaction.
Hence, option (A) is correct: Increase in pressure will favor the forward reaction.
In summary:
(a) Adding more N₂ will favor the forward reaction (F).
(b) Decrease in temperature will favor the forward reaction (D).
(c) Increase in pressure will favor the forward reaction (A).