Problem 88 - A Complete Resource Book in Chemistry for JEE Main

Question

In the reaction: \(\mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]+\mathrm{K}_{2} \mathrm{CO}_{3} \longrightarrow\) the product formed is (a) \(\mathrm{FeCO}_{3}\) (b) \(\mathrm{KCN}\) (c) \(\mathrm{KFeCO}_{3}\) (d) \(\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{4}\right]\)

Step-by-Step Solution

Answer

The product formed is \(\mathrm{FeCO}_{3}\) (option a).

Step 1: Analyze the Reactants

The reactants are \( \text{K}_4[\text{Fe(CN)}_6] \) and \( \text{K}_2\text{CO}_3 \). \( \text{K}_4[\text{Fe(CN)}_6] \) is a complex compound containing iron and cyanide ions, and \( \text{K}_2\text{CO}_3 \) is potassium carbonate.

Step 2: Predict the Reaction Type

Considering the reactants, this reaction would likely involve a double displacement or complexation. Decomposition into simpler products is also possible.

Step 3: Identify Potential Products

Potential products from double displacement reactions involving these reactants could include \( \text{FeCO}_3 \) and \( \text{KCN} \). Given \( \text{KCO}_3 \) can form \( \text{FeCO}_3 \), this is a likely product.

Step 4: Evaluate the Given Options

The options provided are: (a) \( \text{FeCO}_3 \), (b) \( \text{KCN} \), (c) \( \text{KFeCO}_3 \), and (d) \( \text{K}_3[\text{Fe(CN)}_4] \). Based on the typical reactions, \( \text{FeCO}_3 \) is a realistic and stable product.

Step 5: Confirm the Best Option

Option (a) \( \text{FeCO}_3 \) aligns with the expected outcome from the possible interaction of the reactants. Other options do not follow typical chemical behavior for the provided reactants.

Key Concepts

Complex Compounds

Complex compounds are fascinating in the world of inorganic chemistry as they bring together metal ions and various ligands to form a unique structure. Here, we're looking at the complex compound \[ \text{K}_4[ \text{Fe(CN)}_6] \]. This compound unmistakably showcases an iron metal center enveloped by six cyanide ions, which function as ligands.
The ligands, being negatively charged, are attracted to the positively charged iron ion, forming a stable complex. Such compounds often exhibit distinct colors, characteristic shapes, and particular magnetic properties.

• Key elements: Central metal ion (Fe) and ligands (CN⁻).
• The complex ion is \[[\text{Fe(CN)}_6]^{4-} \].
• Potassium (K ext{K}) ions balance the charges in the compound.

This compound is essential in various real-life applications, including electroplating and as reagents in laboratory reactions.

Double Displacement Reactions

In double displacement reactions, two compounds swap components, resulting in new compounds. This type of reaction is often exemplified by the formula:\( AB + CD \rightarrow AD + CB \).It's a common occurrence when ionic compounds in solution react with each other.
In the given exercise, the exchange occurs between \( \text{K}_4[\text{Fe(CN)}_6] \) and \( \text{K}_2\text{CO}_3 \), where the cyanide and carbonate ions could potentially exchange.
The aim is to deduce whether this swapping leads to a stable product. The tendencies of the reacting ions to form bonds and the solubility of potential products are critical considerations. You might see a precipitate form if a product has low solubility in water, which confirms the occurrence of the reaction.

• Reactivity and solubility are pivotal in predicting outcomes.
• Reactions are generally reversible under certain conditions.
• Common examples include precipitation reactions and gas formation.

Chemical Reaction Analysis

Chemical reaction analysis involves understanding how reactants interact to form products. First, it's crucial to identify the types of compounds involved and their potential behavior when mixed. In this case, we analyze the interaction between a complex compound and an ionic salt.
For effective analysis:

• Recognize the chemical nature and roles of each reactant.
• Anticipate type of reaction: Are bonds broken, formed, or both?
• Consider product stability: Stable products are often more favorable.

Through such reactions, each change in chemical bonds dictates new products. Here, rationalizing the transformation of \( \text{K}_4[\text{Fe(CN)}_6] \) with \( \text{K}_2\text{CO}_3 \) helps predict \( \text{FeCO}_3 \) as a likely stable product, aligning with chemical intuition.

Iron Complexes

Iron complexes are pivotal in understanding transition metal chemistry. The example \( \text{Fe(CN)}_6^{4-} \) shows an ion with iron as a central atom surrounded by cyanide ligands.
This structural arrangement offers insights into:

• Geometry: Such complexes often adopt an octahedral shape, contributing to their stability.
• Color and Magnetism: Exhibiting unique colors due to electron transitions and varied magnetic properties due to electron spin configurations.
• Coordination Chemistry: Coordination number and types of bonding define physical and chemical behavior.

Iron being a transition metal can form variable oxidation states, greatly influencing its reactivity and the nature of the complex formed. These properties allow iron complexes to have wide applications in catalysis and biological systems.