Reduction of Manganese Dioxide by HCl
MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O
Overview
Manganese dioxide oxidizes hydrochloric acid to produce chlorine gas, with Mn(IV) being reduced to Mn(II). Two of the four HCl molecules are oxidized (Cl⁻ → Cl₂) while two provide the acid environment. This was historically the main method for chlorine gas production before the chlor-alkali process.
Participants
| Role | Substance | Coefficient | State |
|---|---|---|---|
| Reactant | Hydrochloric Acid HCl | 4 | (aq) |
| Product | Chlorine Cl | 1 | (g) |
| Product | Water H₂O | 2 | (l) |
Everyday Example
This was the reaction Carl Wilhelm Scheele used to discover chlorine gas in 1774, calling it dephlogisticated muriatic acid.
Industrial Importance
Before electrolysis, this was the primary industrial method for chlorine production. It remains a standard lab preparation for small amounts of chlorine gas.
Properties
- Type
- Redox
- Reversible
- No
- Energy
- Exothermic
- ΔH
- -35.0 kJ/mol
Related Reactions
Aqua Regia Dissolving Gold
Bleaching with Sodium Hypochlorite
Cerium(IV) Reduction by Iron(II)
Chlorine Oxidation of Bromide
Chromate-Dichromate Equilibrium
Contact Process SO₂ Oxidation
Copper Displaced by Iron
Copper Oxidation by Nitric Acid
Copper Patina Formation (Verdigris)
Copper Reduction of Silver Ion
Frequently Asked Questions
What is the equation for Reduction of Manganese Dioxide by HCl?
The balanced equation is: MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O.
What type of reaction is Reduction of Manganese Dioxide by HCl?
Reduction of Manganese Dioxide by HCl is a redox reaction.
Is Reduction of Manganese Dioxide by HCl exothermic or endothermic?
Reduction of Manganese Dioxide by HCl is exothermic (releases energy). The enthalpy change (ΔH) is -35.0 kJ/mol.