In water, iron(III) chloride reacts with sodium hydroxide, producing solid iron(III) hydroxide and sodium chloride.
The Correct Answer and Explanation is:
Correct Balanced Chemical Equation:
FeCl₃ (aq) + 3NaOH (aq) → Fe(OH)₃ (s) + 3NaCl (aq)
Explanation:
When iron(III) chloride (FeCl₃) is added to water, it dissolves and dissociates into its constituent ions:
FeCl₃ (aq) → Fe³⁺ (aq) + 3Cl⁻ (aq)
Similarly, sodium hydroxide (NaOH) is a strong base that also dissociates completely in water:
NaOH (aq) → Na⁺ (aq) + OH⁻ (aq)
In solution, the Fe³⁺ ions from iron(III) chloride react with OH⁻ ions from sodium hydroxide. This results in the formation of iron(III) hydroxide, Fe(OH)₃, a reddish-brown precipitate that is insoluble in water:
Fe³⁺ (aq) + 3OH⁻ (aq) → Fe(OH)₃ (s)
At the same time, the Na⁺ and Cl⁻ ions remain in the solution as spectator ions, forming sodium chloride (NaCl), a soluble salt:
Na⁺ (aq) + Cl⁻ (aq) → NaCl (aq)
Thus, the overall balanced molecular equation for the double displacement (also called precipitation reaction) is:
FeCl₃ (aq) + 3NaOH (aq) → Fe(OH)₃ (s) + 3NaCl (aq)
This is a double replacement reaction, where the cations (Fe³⁺ and Na⁺) exchange anions (Cl⁻ and OH⁻), forming a precipitate of Fe(OH)₃.
The net ionic equation, which shows only the species that change during the reaction, is:
Fe³⁺ (aq) + 3OH⁻ (aq) → Fe(OH)₃ (s)
This reaction illustrates key concepts in aqueous chemistry, including ion exchange, solubility rules, and the formation of precipitates. It also demonstrates how certain metal salts can be used to remove heavy metal ions from solutions through precipitation.
