Question

A solution of \[FeC{{l}_{3}}\]​ in water acts as acidic due to______
A. Hydrolysis of $F{{e}^{3+}}$
B. Acidic impurities
C. Dissociation
D. Ionisation

Answer 1

Hint: The oxidation state of iron in ferric chloride, which is a crystal with a dark tint, is +3. It also goes by the name Molysite and has the chemical formula \[FeC{{l}_{3}}\]. The water ionises to hydrogen and hydroxide ions while the ferric chloride in it ionises to iron, or ferric and chloride ions.

Complete Step by Step Solution:
A Lewis acid that coordinates iron is ferric chloride, also known as molysite. It can be made by mixing dichloride and metallic iron. The formula is as follows:
\[2Fe+3C{{l}_{2}}\to 2FeC{{l}_{3}}\]

Now, when ferric chloride is dissolved in water, hydrolysis causes the solution to become acidic. Additionally, water ionises to hydrogen and hydroxide ions while ferric chloride in water solution ionises to iron and chloride ions. These are the equations:
\[FeC{{l}_{3}}\to F{{e}^{+3}}+3C{{l}^{-}}\]
\[{{H}_{2}}O\to {{H}^{+}}+O{{H}^{-}}\]

Additionally, ferric hydroxide will be formed when the ferric ions partially mix with the hydrogen and hydroxide ions. It is a slightly soluble chemical that precipitates as a brown solid. The outcome is as follows:
\[F{{e}^{+3}}+3O{{H}^{-}}\to Fe{{(OH)}_{3}}\]

As a result, the solution becomes more hydrogen ion-rich than it was before the precipitation, which causes the solution to become acidic.
Hence, the correct option A. Hydrolysis of $F{{e}^{3+}}$

Note: In some reactions, ferric chloride is employed in its anhydrous form as a drying agent. Additionally, as a catalyst in organic synthesis, it is employed. Additionally, a ferric chloride test is used to determine whether phenol is present in a particular sample or not. Positive outcomes are produced by substances like enols, oximes, and hydroxamic acids.