2 Ba(OH)2 (aq) + 4 NO2 (l) → Ba(NO2)2 (aq) + Ba(NO3)2 (aq) + 2 H2O (l)

This is an acid-base reaction (neutralization): Ba(OH)2 is a base, NO2 is an acid.

This is an oxidation-reduction (redox) reaction:

2 NIV - 2 e- → 2 NV (oxidation)

2 NIV + 2 e- → 2 NIII (reduction)

NO2 is both an oxidizing and a reducing agent (disproportionation (dismutation)).

Reactants:

  • Ba(OH)2
    • Names: Barium hydroxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Caustic baryta source: wikidata, accessed: 2019-09-02, Barium hydroxide lime source: wikidata, accessed: 2019-09-02, Ba(OH)2 source: wikidata, accessed: 2019-09-02
    • Appearance: White solid source: wikipedia, accessed: 2019-09-27
  • NO2 – Nitrogen dioxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02
    • Other names: Nitrogen(IV) oxide source: wikipedia, accessed: 2019-09-27, Deutoxide of nitrogen source: wikipedia, accessed: 2019-09-27, Nitrogen peroxide source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02
    • Appearance: Brown gas source: wikipedia, accessed: 2019-09-27; Reddish-brown gas or brown or yellow liquid with pungent odour source: ICSC, accessed: 2019-09-04; Yellowish-brown liquid or reddish-brown gas (above 70°F) with a pungent, acrid odor. [Note: In solid form (below 15°F) it is found structurally as N2O4.] source: NIOSH NPG, accessed: 2019-09-02

Products:

  • Ba(NO2)2
    • Names: Barium nitrite source: wikidata, accessed: 2019-09-03
  • Ba(NO3)2
    • Names: Barium nitrate source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04, Barium dinitrate source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Barium salt source: wikipedia, accessed: 2019-09-27
    • Appearance: White, lustrous crystals source: wikipedia, accessed: 2019-09-27; Colourless-to-white crystals or crystalline powder source: ICSC, accessed: 2019-09-04; White, odorless solid. source: NIOSH NPG, accessed: 2019-09-02
  • H2O – Water, oxidane source: wikipedia, accessed: 2019-09-27
    • Other names: Water (H2O) source: wikipedia, accessed: 2019-09-27, Hydrogen hydroxide (HH or HOH) source: wikipedia, accessed: 2019-09-27, Hydrogen oxide source: wikipedia, accessed: 2019-09-27
    • Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas source: wikipedia, accessed: 2019-09-27