Si (s) + 4 HCl (aq) → SiCl₄ (l) + 2 H₂ (g)

This is an oxidation-reduction (redox) reaction:

Si is a reducing agent, HCl is an oxidizing agent.

Reactants:

• Si
  • Names: Silicon , Si , Element 14 ... show moreElemental silicon , [Note: Does not occur freely in nature, but is found in silicon dioxide (silica) and in various silicates.] show less
  • Appearance: Steel-grey crystals or black-to-brown amorphous powder ; Black to gray, lustrous, needle-like crystals. [Note: The amorphous form is a dark-brown powder.]
• 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:

• SiCl₄ – Silicon (IV) chloride
  • Other names: Silicon tetrachloride , Tetrachlorosilane , Silicon chloride
  • Appearance: Colourless liquid ; Colourless clear fuming liquid with pungent odour
• H₂
  • Names: Dihydrogen , Hydrogen , H2 ... show moreH₂ , Molecular hydrogen gas , Hydrogen gas , Hydrogen molecule , Molecular hydrogen show less
  • Appearance: Odourless colourless compressed gas