Problem 105 - A Complete Resource Book in Chemistry for JEE Main

Question

In nitroprusside ion, iron and NO exist as \(\mathrm{Fe}^{\mathrm{ll}}\) and NO \(^{+}\)rather than \(\mathrm{Fe}^{\mathrm{III}}\) and NO. These forms can be differentiated by (a) estimating the concentration of iron (b) measuring the concentration of \(\mathrm{CN}^{-}\) (c) measuring the solid state magnetic moment (d) thermally decomposing the compound

Step-by-Step Solution

Answer

(c) measuring the solid state magnetic moment

Step 1: Understanding the Problem

The nitroprusside ion is being analyzed to determine whether iron and nitric oxide exist as \( \mathrm{Fe}^{\mathrm{II}} \) and NO\( ^{+} \), or as \( \mathrm{Fe}^{\mathrm{III}} \) and NO. We need to differentiate between these oxidation states through various methods.

Step 2: Concept of Coordination Compounds

Nitroprusside ion is a coordination compound where the metal, iron (either in \( \mathrm{Fe}^{\mathrm{II}} \) or \( \mathrm{Fe}^{\mathrm{III}} \) form), is coordinated with the NO ligand. Each form has different physical and chemical properties, particularly with regards to magnetic moments.

Step 3: Considering Magnetic Properties

\( \mathrm{Fe}^{\mathrm{II}} \) generally has a different spin state compared to \( \mathrm{Fe}^{\mathrm{III}} \). Iron's oxidation state affects the compound's magnetic properties. Measuring the solid-state magnetic moment can provide information on the electron configuration and the oxidation state of iron.

Step 4: Analyzing Options

Option (c) is most relevant, as the magnetic moment measurement directly relates to the oxidation state of the central metal ion. The other methods (a, b, and d) do not directly differentiate between the states of iron in the nitroprusside ion.

Key Concepts

Oxidation States

Oxidation states are a crucial concept in chemistry, especially when dealing with coordination compounds. An oxidation state refers to the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. In simpler terms, it represents the number of electrons an atom gains, loses, or appears to gain or lose when it forms a compound.

In the context of the nitroprusside ion, determining whether iron is in the oxidation state of +2 (Fe\(^{II}\)) or +3 (Fe\(^{III}\)) is vital. The oxidation state of iron affects its chemical behavior and the overall properties of the compound.

• Fe\(^{II}\): carries a +2 charge, meaning it has lost two electrons.
• Fe\(^{III}\): carries a +3 charge, indicating a loss of three electrons.

The distinction between these states affects how the compound interacts with ligands and influences its reactivity, color, and magnetic properties. Oxidation states serve as a foundational feature for understanding many chemical reactions and properties.

Magnetic Properties

The magnetic properties of a coordination compound are intrinsically linked to its electron configuration and oxidation state. Magnetism in coordination compounds stems from unpaired electrons, and the presence or absence of these unpaired electrons determines whether a substance is paramagnetic (attracted to a magnetic field) or diamagnetic (repelled by a magnetic field).

For iron in coordination compounds, the oxidation state plays a pivotal role in its magnetic properties.

• Fe\(^{II}\) typically has four unpaired electrons in a high-spin state, making it paramagnetic.
• Fe\(^{III}\), on the other hand, often has five unpaired electrons in a high-spin state, enhancing its paramagnetic character.

By measuring the solid-state magnetic moment, scientists can infer the electron configuration of iron within the compound. If the compound exhibits certain magnetic behavior, it confirms the oxidation state and the arrangement of the d-electrons around the metal center. This property is key in distinguishing between different forms of iron within coordination complexes.

Iron Complexes

Iron complexes are a fascinating aspect of coordination chemistry, where iron acts as a central metal atom bonded to surrounding ligands. The nature of these ligands, as well as the oxidation state of the iron, significantly influences the properties of the complex.

Iron can form complexes with numerous ligands such as CN\(^{-}\) and NO, each affecting the complex's stability and reactivity.

• In a low oxidation state, iron tends to form more stable coordination complexes.
• The ligand type affects the electronic structure, thereby influencing magnetic, optical, and electronic properties.

Iron's versatile oxidation states allow it to participate in a variety of chemical processes, making it essential in biochemical pathways, catalytic cycles, and industrial applications. The study of iron complexes not only helps us understand fundamental chemistry but also their role in real-world applications and the synthesis of new materials.