Le Chatelier's principle determines equilibrium shifts Steps:

• The reaction 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) is exothermic (ΔH = -196 kJ/mol), with 3 moles of gas on left and 2 on right.
• Adding O₂ increases reactant concentration, shifting equilibrium right to consume it.
• Adding SO₃ increases product concentration, shifting equilibrium left to consume it.
• Increasing pressure favors fewer gas moles (right side), shifting right; increasing temperature favors endothermic direction (left).

Why B and D are correct:

• B: Adding SO₃ raises product concentration, so equilibrium shifts left per Le Chatelier's principle to counteract the change.
• D: For exothermic reaction, increasing temperature shifts equilibrium left (endothermic direction) to absorb heat, per Le Chatelier's principle.

Why the others are wrong:

• A: Adding O₂ raises reactant concentration, shifting equilibrium right.
• C: Increasing pressure shifts equilibrium right toward fewer gas moles.

Final answer: B and D