H₂O₂ + 2 HI → I₂ + 2 H₂O

This is an oxidation-reduction (redox) reaction:

HI is a reducing agent, H₂O₂ is an oxidizing agent.

Reactants:

• H₂O₂ – Hydrogen peroxide
  • Other names: Dioxidane , Oxidanyl , Perhydroxic acid ... show more0-hydroxyol , Dihydrogen dioxide , Oxygenated water , Peroxaan , Hydrogen peroxide (>60% solution in water) , H2O2 , Peroxide , Hydroperoxide , Hydrogen dioxide , High-strength hydrogen peroxide , Hydrogen peroxide (aqueous) show less
  • Appearance: Very light blue color; colorless in solution ; Colourless liquid ; Colorless liquid with a slightly sharp odor. [Note: The pure compound is a crystalline solid below 12°F. Often used in an aqueous solution.]
• HI – Iodane
  • Other names: Hydroiodic acid , Hydrogen iodide , Hydronium iodide ... show moreHI , Anhydrous hydriodic acid show less
  • Appearance: Colorless liquid ; Colorless gas ; Colourless compressed liquefied gas with pungent odour

Products:

• I₂
  • Names: Iodine , Jod , Iode ... show moreIodio , Yodo , Iodine crystals , Molecular iodine show less
  • Appearance: Bluish black or dark purple crystals with pungent odour ; Violet solid with a sharp, characteristic odor.
• H₂O – Water, oxidane
  • Other names: Water (H2O) , Hydrogen hydroxide (HH or HOH) , Hydrogen oxide ... show moreDihydrogen monoxide (DHMO) (systematic name) , Hydrogen monoxide , Dihydrogen oxide , Hydric acid , Hydrohydroxic acid , Hydroxic acid , Hydrol , Μ-oxido dihydrogen , Κ1-hydroxyl hydrogen(0) show less
  • Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas