2 HCl (aq) + Na2S2O3 (aq) → H2O (l) + S (s) + SO2 (aq) + 2 NaCl (aq)
This is an oxidation-reduction (redox) reaction:
SII + 2 e- → S0 (reduction)
SII - 2 e- → SIV (oxidation)
Na2S2O3 is both an oxidizing and a reducing agent (disproportionation (dismutation)).
This is a precipitation reaction: S is the formed precipitate.
- HCl – Chlorane , Hydrogen chloride
- Other names: Hydrochloric acid , Hydrochloric acid gas , HCl
- 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.]
- H2O – Water, oxidane
- SO2 – Sulfur dioxide
- Other names: Sulfurous anhydride , Sulphur dioxide , Sulfurous acid anhydride
- Appearance: Colorless gas ; Colourless gas or compressed liquefied gas with pungent odour ; Colorless gas with a characteristic, irritating, pungent odor. [Note: A liquid below 14°F. Shipped as a liquefied compressed gas.]
- NaCl – Sodium chloride