Iron reacts with dry hydrogen chloride gas to produce iron(II) chloride (ferrous chloride) and hydrogen gas.
The Chemical Reaction
The reaction can be represented by the following balanced chemical equation:
Fe(s) + 2 HCl(g) → FeCl₂(s) + H₂(g)
- Fe(s): Solid iron
- HCl(g): Hydrogen chloride gas
- FeCl₂(s): Solid iron(II) chloride
- H₂(g): Hydrogen gas
Explanation of the Reaction
This is a single displacement redox reaction. Iron (Fe) is oxidized, losing two electrons to form iron(II) ions (Fe²⁺). Hydrogen ions (H⁺) from the hydrogen chloride are reduced, gaining electrons to form hydrogen gas (H₂). The chloride ions (Cl⁻) act as spectator ions, combining with the iron(II) ions to form iron(II) chloride.
Key Points
- The reaction requires anhydrous (dry) conditions. If water is present, the hydrogen chloride will dissolve to form hydrochloric acid, and the reaction mechanism may differ slightly, although the products will be the same.
- The iron(II) chloride produced is a solid under normal reaction conditions.
- The reaction proceeds readily at elevated temperatures.
- The reaction is exothermic, meaning it releases heat.
Differences from Reaction with Hydrochloric Acid (Aqueous HCl)
While the products are the same, reacting iron with dry hydrogen chloride gas is different from reacting it with hydrochloric acid (aqueous HCl). With HCl(aq), the reaction is more complex due to the presence of water, involving the formation of hydrated iron(II) ions. The dry gas reaction provides a cleaner pathway to anhydrous iron(II) chloride.
