2 ClO₂ (g) + 2 NaOH (aq) → NaClO₃ (aq) + NaClO₂ (aq) + H₂O (l)

This is an oxidation-reduction (redox) reaction:

ClO₂ is both an oxidizing and a reducing agent (disproportionation (dismutation)).

Reactants:

• ClO₂ – Chlorine dioxide , 4-chlorane (substitutive) OR Dioxidochlorine(•) (additive) -->
  • Other names: Chlorine(IV) oxide , Chlorine oxide , Chlorine peroxide ... show moreO2Cl(.) , [ClO2](.) , (OClO)(.) , Chlorine(IV)oxide show less
  • Appearance: Yellow to reddish gas ; Red-yellow gas with pungent odour ; Yellow to red gas or a red-brown liquid (below 52°F) with an unpleasant odor similar to chlorine and nitric acid.
• NaOH
  • Names: Sodium hydroxide , Caustic soda , Lye ... show moreSoda lye , Sodium hydrate , NaOH , White caustic , Lye [Sodium hydroxide] show less
  • Appearance: White, waxy, opaque crystals ; White hygroscopic solid in various forms ; Colorless to white, odorless solid (flakes, beads, granular form).

Products:

• NaClO₃ – Sodium chlorate
  • Other names: Sodium chlorate(V) , Chloric acid, sodium salt
  • Appearance: Colorless or white solid, hygroscopic ; Odourless colourless crystals or white granules
• NaClO₂ – Sodium chlorite
  • Other names: Chlorous acid , Sodium salt , Textone ... show moreNaO2Cl , NaClO2 , Chlorous acid, sodium salt , Chlorite sodium show less
  • Appearance: White solid ; Slightly hygroscopic white crystals or flakes
• 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