What is the oxidation half reaction in the chemical reaction cr2o72 - (aq) + 6 cl - (aq) + 14 h + (aq) → 2 cr3 + (aq) + 3 cl2 (aq) + 7 h2o (l) ?

The complete equation for the reaction is

Cr₂O₇²⁻ + 6Cl⁻ + 14H⁺ - - - > 2Cr³⁺ + 3Cl₂ + 7H₂O

in the oxidation half reaction the oxidation number of the species increases.

in the reduction half reaction the oxidation number of the species decreases.

the oxidation number of Cr reduces from + 6 in Cr₂O₇²⁻ to + 3 in Cr³⁺

the oxidation number of Cl increases from - 1 in Cl⁻ to Cl₂ therefore oxidation takes place

oxidation half reaction is as follows

2Cl⁻ - - > Cl₂ + 2e