As₂O₃ + 3I₂ → AsI₃ + 3O₂
In this reaction, arsenic trioxide acts as the reducing agent, donating electrons to iodine, which acts as the oxidizing agent, accepting electrons. Arsenic changes its oxidation state from +3 in As₂O₃ to +3 in AsI₃, while iodine changes its oxidation state from 0 in I₂ to -1 in AsI₃.
The reaction between arsenic trioxide and iodine is typically carried out by heating a mixture of the two reactants in a closed vessel. The reaction proceeds through a series of intermediate steps, ultimately leading to the formation of AsI₃ and O₂.
