In the reaction 2Fe³⁺ + Sn²⁺ → 2Fe²⁺ + Sn⁴⁺, what is the equivalent weight of Fe³⁺ if the molecular weight is 55.85 g/mol?
Correct: D
The oxidation state of Fe decreases from +3 to +2, gaining 1 electron per Fe ion. The equivalent weight is molecular weight divided by n-factor (1). Thus, 55.85/1 = 55.85 g/equivalent. Common mistake: Confusing n-factor with change in oxidation state for multiple atoms.