Problem 51 - A Complete Resource Book in Chemistry for JEE Main

Question

What product is formed by mixing the solution of \(\mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]\) with the solution of \(\mathrm{FeCl}_{2} ?\) (a) ferric ferrocyanide (b) ferri ferricyanide (c) ferro ferricyanide (d) none of these

Step-by-Step Solution

Answer

The product formed is ferric ferrocyanide, answer (a).

Step 1: Write the Chemical Equations

First, identify the reactants involved in the chemical process: potassium ferrocyanide, \( \mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right] \), and iron(II) chloride, \( \mathrm{FeCl}_{2} \). The typical reaction between these involves the exchange of ions.

Step 2: Identify Ion Exchange

Both reactants are known to undergo an ion exchange, where iron ions form a complex compound with the ferrocyanide ions, producing a precipitate.

Step 3: Determine Product Formation

The reaction typically forms an insoluble compound known as iron(III) ferrocyanide, commonly referred to as Prussian Blue, with the formula \( \mathrm{Fe}_{4}[\mathrm{Fe}(\mathrm{CN})_{6}]_{3} \). This compound is synonymous with ferric ferrocyanide.

Step 4: Confirm Product Identity

The formation of a blue-colored precipitate when these solutions are mixed confirms the identity of the product as ferric ferrocyanide. This matches the description choice (a) in the options provided.

Key Concepts

Ionic Exchange

Ionic exchange is a fundamental concept in chemistry where ions are swapped between two reactants. In the exercise provided, potassium ferrocyanide and iron(II) chloride undergo such a process.

• When these two compounds mix, their ions rearrange themselves to form a new substance.
• This rearrangement involves iron ions trading places, which significantly changes the resulting compounds.

By understanding ionic exchange, you can predict the products formed in various chemical reactions. In our specific reaction, the exchange leads to the formation of a beautiful blue compound, illustrating the impact of ion rearrangement.

Complex Compounds

Complex compounds are chemical structures that consist of a central metal atom bonded to surrounding molecules or ions. These structures are often more stable and have unique properties.
In our exercise, iron ions form a complex compound with ferrocyanide ions.

• The central metal atom here is iron (Fe), and the surrounding ions are cyanides (CN).
• Such compounds can have intriguing appearances and behaviors due to their intricate structures.

Complex compounds are crucial in many fields, from medicinal chemistry to materials science. They often exhibit distinct colors, as seen with the Prussian Blue formed in this reaction.

Insoluble Compounds

Insoluble compounds are those that do not dissolve well in water. Their formation is typically indicated by a solid precipitate in the reaction.

• In the described chemical reaction, the result is iron(III) ferrocyanide, which is insoluble, forming a solid precipitate.
• This solid appears as a distinct phase separate from the liquid solution, emphasizing its insolubility.

The presence of an insoluble compound can often be detected by changes in solution clarity or color. In this exercise, the insolubility of the product results in the visible formation of Prussian Blue, recognizable by its distinctive deep blue color.

Prussian Blue

Prussian Blue is an iconic blue pigment formed through a fascinating chemical process. In this reaction, when potassium ferrocyanide meets iron(II) chloride, Prussian Blue materializes as a precipitate.

• Known scientifically as iron(III) ferrocyanide, it boasts a complex structure with a vibrant blue hue.
• This compound has been used historically in paints, inks, and even medical applications due to its color and properties.

Prussian Blue exemplifies how chemistry can create something both scientifically interesting and aesthetically pleasing. Observing the formation of this compound provides insight into how particular combinations of elements lead to innovative and notable substances.