Question

Molten CuBr2 is electrolyzed.

Which reaction occurs at the anode?

2e– + Cu2+(l) → Cu(l)
Oxidation occurs at the anode. In oxidation, reactants gain electrons. In this reaction, Cu2+ gains electrons and becomes metallic Cu.

2Br–(l) → Br2(g) + 2e–
Oxidation occurs at the anode. In oxidation, reactants lose electrons. In this reaction, Br– loses electrons and becomes Br2 gas.

Br2(g) + 2e– → 2Br–(l)
Oxidation occurs at the anode. In oxidation, reactants gain electrons. In this reaction, Br2 gas gains electrons and becomes Br– ions.

Cu(l) → 2e– + Cu2+(l)
Oxidation occurs at the anode. In oxidation, reactants lose electrons. In this reaction, metallic Cu loses electrons and becomes Cu2+ ions.

Answer 1

Why don't you write out the equation of the electrolysis?
CuBr2 ==> Cu + 2Br^-
Cu changes oxidation state from 2+ to 0 so it gains electrons. Right?
2Br^- ==> Br2(l)
Br changes oxidation state from a total of 2- to 0 so it loses electrons. Right?
And the definition: Oxidation occurs at the anode.
ipso facto