2 NaClO3 (aq) + SO2 (aq) + H2SO4 (aq) → 2 ClO2 (g) + 2 NaHSO4 (aq)

This is an oxidation-reduction (redox) reaction:

SIV - 2 e- → SVI (oxidation)

2 ClV + 2 e- → 2 ClIV (reduction)

SO2 is a reducing agent, NaClO3 is an oxidizing agent.

This is a gas evolution reaction, ClO2 is the formed gas.

Reactants:

  • NaClO3 – Sodium chlorate source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04
    • Other names: Sodium chlorate(V) source: wikipedia, accessed: 2019-09-27, Chloric acid, sodium salt source: ICSC, accessed: 2019-09-04
    • Appearance: Colorless or white solid, hygroscopic source: wikipedia, accessed: 2019-09-27; Odourless colourless crystals or white granules source: ICSC, accessed: 2019-09-04
  • SO2 – Sulfur dioxide source: wikipedia, accessed: 2019-09-28source: wikidata, accessed: 2019-09-02source: NIOSH NPG, accessed: 2019-09-02
    • Other names: Sulfurous anhydride source: wikipedia, accessed: 2019-09-28source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04, Sulphur dioxide source: ICSC, accessed: 2019-09-04source: wikidata, accessed: 2019-09-02, Sulfurous acid anhydride source: wikidata, accessed: 2019-09-02source: NIOSH NPG, accessed: 2019-09-02
    • Appearance: Colorless gas source: wikipedia, accessed: 2019-09-28; Colourless gas or compressed liquefied gas with pungent odour source: ICSC, accessed: 2019-09-04; Colorless gas with a characteristic, irritating, pungent odor. [Note: A liquid below 14°F. Shipped as a liquefied compressed gas.] source: NIOSH NPG, accessed: 2019-09-02
  • H2SO4 – Sulfuric acid source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-07source: NIOSH NPG, accessed: 2019-09-02
    • Other names: Oil of vitriol source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-07source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Sulfuric acid, concentrated (> 51% and < 100%) source: ICSC, accessed: 2019-09-04, H2SO4 source: wikidata, accessed: 2019-09-07
    • Appearance: Clear, colorless liquid source: wikipedia, accessed: 2019-09-27; Odourless colourless oily hygroscopic liquid source: ICSC, accessed: 2019-09-04; Colorless to dark-brown, oily, odorless liquid. [Note: Pure compound is a solid below 51°F. Often used in an aqueous solution.] source: NIOSH NPG, accessed: 2019-09-02

Products:

  • ClO2 – Chlorine dioxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, 4-chlorane (substitutive) OR Dioxidochlorine(•) (additive) --> source: wikipedia, accessed: 2019-09-27
    • Other names: Chlorine(IV) oxide source: wikipedia, accessed: 2019-09-27, Chlorine oxide source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Chlorine peroxide source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02
    • Appearance: Yellow to reddish gas source: wikipedia, accessed: 2019-09-27; Red-yellow gas with pungent odour source: ICSC, accessed: 2019-09-04; Yellow to red gas or a red-brown liquid (below 52°F) with an unpleasant odor similar to chlorine and nitric acid. source: NIOSH NPG, accessed: 2019-09-02
  • NaHSO4 – Sodium hydrogen sulfate source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Other names: Sodium bisulfate source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Sodium acid sulfate source: wikipedia, accessed: 2019-09-27, Bisulfate of soda source: wikipedia, accessed: 2019-09-27
    • Appearance: White solid source: wikipedia, accessed: 2019-09-27