Question

What happens when iron filings are added to dilute hydrochloric acid?

• A. Only hydrogen gas is produced
• B. Hydrogen gas and iron (II) chloride are formed
• C. Hydrogen gas and iron (III) chloride are formed
• D. Iron filings do not react

Answer 1

The correct option is C Hydrogen gas and iron (III) chloride are formed

In an aqueous solution, the hydrochloric acid dissociates to render hydronium ions and chloride ions. The released chloride ions oxidize the iron atoms to form iron (III) chloride as ${\text{Fe}}^{3+}$ ions are more stable than ${\text{Fe}}^{2+}$ ions. The hydrogen ions are reduced to hydrogen gas. Here, the reduction is observed in terms of the gain of electrons and the oxidation is observed in terms of the loss of electrons. Hence, hydrogen gas and iron (III) chloride are produced.