Le Chatelier's principle predicts pressure and temperature effects on ammonia yield

Steps:

• Reaction has fewer gas moles on product side (1 vs. 4), so higher pressure shifts equilibrium right, increasing % NH₃.
• Exothermic forward reaction (ΔH negative), so higher temperature shifts equilibrium left, decreasing % NH₃.
• At 250°C (lower T), equilibrium favors products more, so % NH₃ starts higher and rises faster with pressure.
• At 350°C (higher T), % NH₃ starts lower and rises more slowly with pressure.

Why B is correct:

• Matches Le Chatelier's principle: steeper % NH₃ increase at lower temperature due to greater exothermic favorability.

Why the others are wrong:

• A: Reverses temperature effect, showing higher yield at 350°C.
• C: Ignores pressure effect, showing flat or minimal change.
• D: Inverts pressure trend, decreasing % NH₃ with higher pressure.

Final answer: B