3 H₂SeO₄ + 2 Au + 8 HCl → 2 H[AuCl₄] + 3 SeO₂ + 6 H₂O

This is a complexation reaction: H[AuCl₄] is the formed complex.

This is an oxidation-reduction (redox) reaction:

H₂SeO₄ is an oxidizing agent, Au is a reducing agent.

Reactants:

• H₂SeO₄ – Selenic(VI) acid
  • Other names: Selenic acid , H2SeO4 , [SeO2(OH)2]
  • Appearance: Colorless deliquescent crystals
• Au
  • Names: Gold , Au , Element 79 , Aurum
• HCl – Chlorane , Hydrogen chloride
  • Other names: Hydrochloric acid , M , Uriatic acid ... show moreHydronium chloride , Chlorhydric Acid , Hydrochloric acid gas , HCl , Anhydrous hydrogen chloride , Hydrochloric acid, anhydrous , Aqueous hydrogen chloride , [Note: Often used in an aqueous solution.] show less
  • Appearance: Colorless, transparent liquid, fumes in air if concentrated ; Colorless gas ; Colourless compressed liquefied gas with pungent odour ; Colorless to slightly yellow gas with a pungent, irritating odor. [Note: Shipped as a liquefied compressed gas.]

Products:

• H[AuCl₄]
  • Names: Chloroauric acid , Hydrogen tetrachloroaurate , Chlorauric acid ... show moreAurochloric acid , Aurate(1−) , Tetrachloro- , Hydrogen , (SP-4-1)- , Hydrogen aurichloride show less
  • Appearance: Orange-yellow needle-like crystals | hygroscopic
• SeO₂
  • Names: Selenium dioxide , Selenium(IV) oxide , Selenous anhydride ... show moreSelenious anhydride , Selenium oxide show less
  • Appearance: White crystals, turn slightly pink with trace decomposition ; Lustrous white hygroscopic crystals or powder. its yellowish green vapour has a pungent sour smell
• 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