Cr₂O₇^2–(aq) + Cl^–(aq) → Cr³⁺(aq) + Cl₂(g)

acidic environment

Cr₂O₇^2–(aq) + 14 H⁺(aq) + 6 e^– → 2 Cr³⁺(aq) + 7 H₂O(l)

[2 Cl^–(aq) → Cl₂(g) + 2 e^–] × 3

sum and eliminate common species

Cr₂O₇^2–(aq) + 6 Cl^–(aq) + 14 H⁺(aq) → 2 Cr³⁺(aq) + 3 Cl₂(g) + 7 H₂O(l)