# Reaction of Iron with Concentrated and dilute hydrochloric acid

Does Iron react differently with dilute and concentrated hydrochloric acid? A. I know that with dilute hydrochloric acid Iron (II) chloride is formed. B. I read on the internet that with concentrated hydrochloric acid Iron reacts to form Iron (III) Chloride. Could someone tell me: 1. Is FeCl3 formed as a product of reaction between HCl (conc.) and iron? 2. If yes, then what is the complete chemical reaction?

Thank you.

• – user7951
Jul 29 '16 at 13:41

No, $\ce{FeCl3}$ is not formed upon reaction with Conc. $\ce{HCl}$. Both dilute and concentrated $\ce{HCl}$ give $\ce{FeCl2}$ as product.
$$\ce{Fe + 2HCl_{dil} -> Fe^2+ + 2Cl^- + H2 ^}$$ $$\ce{Fe + 2HCl_{conc} -> Fe^2+ + 2Cl^- + H2 ^}$$
• @DatBoi Hydrogen prevents oxidation from $\ce{Fe^2+}$ to $\ce{Fe^3+}$. Refer to the previous question: "Acids can oxidize iron since the redox potentials E for pH=0 show that $\ce{H+}$ can oxidize iron to $\ce{Fe^2+}$ but non-oxidizing acids (in this case HCl) cannot further oxidize $\ce{Fe^2+}$ to $\ce{Fe^3+}$." If there is presence of oxygen, it can oxidize to $\ce{Fe^3+}$. Jan 22 at 7:27