Here's the balanced chemical equation:
FeCl₃(aq) + 3NH₄SCN(aq) ⇌ [Fe(SCN)₃]²⁻(aq) + 3NH₄Cl(aq)
Explanation:
* Reactants:
* Iron(III) chloride (FeCl₃) is a pale yellow solution.
* Ammonium thiocyanate (NH₄SCN) is a colorless solution.
* Products:
* [Fe(SCN)₃]²⁻: This is the iron(III) thiocyanate complex ion, which forms a deep blood-red solution. This complex formation is the driving force of the reaction.
* Ammonium chloride (NH₄Cl) remains in solution and is colorless.
Key points:
* The reaction is reversible, meaning the products can react to form the reactants again. This is indicated by the double arrow (⇌).
* The reaction is favored in the forward direction, meaning the formation of the red complex ion is more likely to occur. This is because the complex ion is very stable.
* The color change from pale yellow to blood-red is a visual indication of the reaction taking place.
Applications:
This reaction has various applications, including:
* Chemical analysis: The intensity of the red color can be used to determine the concentration of iron ions in a solution.
* Demonstrations: It's a common demonstration in chemistry classes to illustrate the concepts of equilibrium, complex ion formation, and color change.
