Le Chatelier's principle applied to temperature and pressure shifts

Steps:

• Identify that darker color means more brown NO₂, so equilibrium shifts left (reverse).
• For temperature: forward is exothermic, so increasing T favors endothermic reverse (more NO₂).
• For pressure: 2 moles NO₂ vs. 1 mole N₂O₄, so decreasing P favors side with more moles (left, more NO₂).
• Combine: increase T and decrease P both shift left, increasing NO₂.

Why C is correct:

• Le Chatelier's principle: increasing temperature opposes heat by favoring endothermic direction (reverse); decreasing pressure favors more moles of gas (reactants).

Why the others are wrong:

• A: Decreasing temperature favors exothermic forward (less NO₂); decreasing pressure favors reverse, but net shift unclear or not darker.
• B: Decreasing temperature favors forward (less NO₂); increasing pressure favors fewer moles (forward, less NO₂).
• D: Increasing temperature favors reverse (more NO₂); increasing pressure favors forward (less NO₂), opposing effects.

Final answer: C