When iron(III) chloride (FeCl₃) is mixed with ammonia (NH₃), a fascinating reaction occurs resulting in the formation of a rust-colored precipitate and the release of hydrogen chloride gas (HCl). Let's break down the process:

1. Formation of Iron(III) Hydroxide:

* Ammonia (NH₃) acts as a base and reacts with iron(III) chloride (FeCl₃), leading to the formation of iron(III) hydroxide (Fe(OH)₃).

Equation:

FeCl₃ (aq) + 3 NH₃ (aq) + 3 H₂O (l) → Fe(OH)₃ (s) + 3 NH₄Cl (aq)

2. Precipitation:

* Iron(III) hydroxide (Fe(OH)₃) is insoluble in water, so it precipitates out of the solution as a solid. This solid appears as a rust-colored precipitate.

3. Release of Hydrogen Chloride Gas:

* During the reaction, hydrogen chloride gas (HCl) is also released as a byproduct. This gas can be recognized by its pungent odor.

The Overall Reaction:

FeCl₃ (aq) + 3 NH₃ (aq) + 3 H₂O (l) → Fe(OH)₃ (s) + 3 NH₄Cl (aq) + HCl (g)

Important Note:

* The reaction between iron(III) chloride and ammonia is highly exothermic, meaning it releases heat.

* The precipitate formed can be further reacted with excess ammonia to form a complex ion, [Fe(NH₃)₆]³⁺.

In summary, when iron(III) chloride is mixed with ammonia, a rust-colored precipitate of iron(III) hydroxide forms along with hydrogen chloride gas. This reaction is a classic example of a precipitation reaction driven by the formation of an insoluble product.