🧪 Chemistry · Redox Reactions · NEET & JEE

In the ion-electron method of balancing, when balancing the following half-reaction in acidic medium: Cr2O72- → Cr3+, how many electrons are transferred?

Answer: 6.

A 3
B 5
C 6
D 12

Correct answer: C. 6

Explanation: Each Cr goes from +6 to +3 (gains 3e⁻). There are 2 Cr atoms in Cr₂O₇²⁻, so total electrons gained = 2 × 3 = 6.

Electron transfer in a redox reaction: zinc loses electrons (oxidised, acts as reducing agent) and copper(II) ions gain those same electrons (reduced, acts as oxidising agent).

Concept context

Master electron transfer in chemistry: assign oxidation states, balance half-reactions, identify oxidising and reducing agents, and connect redox to everyday reactions.

Read the full Redox Reactions notes →

In the ion-electron method of balancing, when balancing the following half-reaction in acidic medium: Cr<sub>2</sub>O<sub>7</sub><sup>2-</sup> → Cr<sup>3+</sup>, how many electrons are transferred?

Concept context

More Redox Reactions questions