Concept:Note: Historically, this past paper question was printed with a missing stem. Based on the official answer key (D), the implied question was: "Which of the following conditions shifts the equilibrium in the backward (reactant) direction?"Formula:$$ \text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3 \quad \Delta H < 0 $$
Solution:- According to Le Chatelier's Principle, adding a product to an equilibrium mixture forces the system to consume the excess.
- Continuous addition of \( \text{NH}_3 \) creates an excess on the product side.
- The system shifts in the reverse (backward) direction to consume the added \( \text{NH}_3 \), turning it back into \( \text{N}_2 \) and \( \text{H}_2 \).
Why other options are incorrect:Low temperature and continuous removal of \( \text{NH}_3 \) (Options A and C) would shift the reaction forward to maximize yield, which are the standard industrial conditions (Haber Process).
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