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Problem 6 - Olympiad

What is the change in pH when 1 mole of Fe³⁺ is reduced to Fe²⁺ in 1 L solution if 0.5 moles are reduced?

A. Remains sameB. Increases by 0.3C. Decreases by 0.3D. Increases by 0.9

Correct: A

Fe³⁺ + e⁻ → Fe²⁺ (no H+ or OH- involved). Since H+ concentration isn’t affected directly, pH remains unchanged. Common confusion: Assuming redox affects water autoionization unless specified.