6 KNO₂ (aq) + 3 H₂SO₄ (aq) → 2 HNO₃ (aq) + 4 NO (g) + 3 K₂SO₄ (aq) + 2 H₂O (l)

This is an oxidation-reduction (redox) reaction:

KNO₂ is both an oxidizing and a reducing agent (disproportionation (dismutation)).

This is a gas evolution reaction, NO is the formed gas.

Reactants:

• KNO₂
  • Names: Potassium nitrite , Nitrous acid potassium salt
  • Appearance: White or slight yellow solid | deliquescent ; White-to-yellow deliquescent solid in various forms
• H₂SO₄ – Sulfuric acid
  • Other names: Oil of vitriol , Sulfuric acid, concentrated (> 51% and < 100%) , H2SO4 ... show moreSulphuric acid , Battery acid , Hydrogen sulfate , [SO2(OH)2] , [S(OH)2O2] , Sulfuric acid (aqueous) show less
  • Appearance: Clear, colorless liquid ; Odourless colourless oily hygroscopic liquid ; Colorless to dark-brown, oily, odorless liquid. [Note: Pure compound is a solid below 51°F. Often used in an aqueous solution.]

Products:

• HNO₃ – Nitric acid
  • Other names: Aqua fortis , Spirit of niter , Eau forte ... show moreHydrogen nitrate , Acidum nitricum , Nitric acid (> 70% in water) , Fuming nitric acid , Engravers acid , HONO2 , Red fuming nitric acid , RFNA , White fuming nitric acid (WFNA) show less
  • Appearance: Colorless, yellow or red fuming liquid ; Colourless-to-yellow liquid with pungent odour ; Colorless, yellow, or red, fuming liquid with an acrid, suffocating odor. [Note: Often used in an aqueous solution. Fuming nitric acid is concentrated nitric acid that contains dissolved nitrogen dioxide.]
• NO – Nitrogen monoxide , Oxidonitrogen(•) (additive)
  • Other names: Nitric oxide , Nitrogen(II) oxide , Nitric oxide (radical) ... show moreMononitrogen monoxide , (.)NO , EDRF , Nitrogen monooxide , [NO] , Oxido de nitrogeno(ii) , NO(.) , Oxido nitrico , Stickstoff(ii)-oxid , NO , Oxyde azotique , Oxyde nitrique , Stickstoffmonoxid , Nitrosyl , (NO)(.) , Monoxido de nitrogeno , Endothelium-derived relaxing factor , Nitroxide radical , Nitroxyl , Nitrosyl radical , Hydroxyamine , Nitrogen oxide , Nitrogen protoxide , Nitrosyl hydride , Nitric Oxide show less
  • Appearance: Colourless gas ; Colourless compressed gas ; Colorless gas. [Note: Shipped as a nonliquefied compressed gas.]
• K₂SO₄
  • Names: Potassium sulfate , Potassium sulphate , Dipotassium sulfate ... show moreKaliumsulfat , K2SO4 , Sulfuric acid dipotassium salt show less
  • Appearance: White solid ; Colourless-to-white crystals
• 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