2 HCl (aq) + H₂O₂ (aq) + CuS (s) → 2 H₂O (l) + S (s) + CuCl₂ (aq)

This is an oxidation-reduction (redox) reaction:

CuS is a reducing agent, H₂O₂ is an oxidizing agent.

Reactants:

• 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.]
• H₂O₂ – Hydrogen peroxide
  • Other names: Dioxidane , Oxidanyl , Perhydroxic acid ... show more0-hydroxyol , Dihydrogen dioxide , Oxygenated water , Peroxaan , Hydrogen peroxide (>60% solution in water) , H2O2 , Peroxide , Hydroperoxide , Hydrogen dioxide , High-strength hydrogen peroxide , Hydrogen peroxide (aqueous) show less
  • Appearance: Very light blue color; colorless in solution ; Colourless liquid ; Colorless liquid with a slightly sharp odor. [Note: The pure compound is a crystalline solid below 12°F. Often used in an aqueous solution.]
• CuS – Copper sulfide
  • Other names: Copper monosulfide , Covellite , Copper(II) sulfide , Cupric sulfide
  • Appearance: Black powder or lumps

Products:

• 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
• S
  • Names: Sulfur , S , Sulphur ... show moreElement 16 , Flowers of sulfur , Flour sulfur , Brimstone show less
  • Appearance: Yellow solid in various forms
• CuCl₂
  • Names: Copper(II) chloride , Cupric chloride , Copper chloride ... show moreCopper(2+) chloride , Cupric chloride anhydrous , Coclor , Copper(II) chloride (1:2) , Copper chloride (CuCl2) , Cupric dichloride , Copper(2+)chloride , Copper dichloride , Copper bichloride , CuCl2 , Cupric Chloride show less
  • Appearance: Yellow-brown solid (anhydrous) | blue-green solid (dihydrate)