Balance the following redox equation: PbBr₂ + FeBr₃ → PbBr₄ + FeBr₂
A) PbBr₂ + 3 FeBr₃ → PbBr₄ + 3 FeBr₂
B) PbBr₂ + 2 FeBr₃ → PbBr₄ + 2 FeBr₂
C) 3 PbBr₂ + FeBr₃ → 3 PbBr₄ + FeBr₂
D) 2 PbBr₂ + FeBr₃ → 2 PbBr₄ + FeBr₂
E) 2 PbBr₂ + 3 FeBr₃ → 2 PbBr₄ + 3 FeBr₂
IMAT 2026 · Question 39
Q39 - Oxidation and reduction
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The correct answer is B) PbBr₂ + 2 FeBr₃ → PbBr₄ + 2 FeBr₂.
Find the oxidation numbers (Br is always −1 here):
Pb: +2 → +4, so each Pb loses 2 e⁻
Fe: +3 → +2, so each Fe gains 1 e⁻
To balance electrons, we need 2 Fe for every Pb.
Check bromine: left 2 + 2 × 3 = 8; right 4 + 2 × 2 = 8. Balanced.
In A and E, the electrons gained do not equal the electrons lost. In C and D, Pb is in excess and the bromine count fails.
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