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

Question

In nitroprusside ion, iron and NO exist as \(\mathrm{Fe}^{\mathrm{II}}\) and \(\mathrm{NO}^{+}\)rather than \(\mathrm{Fe}^{\mathrm{ll}}\) and \(\mathrm{NO}\). 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

The solid state magnetic moment measurement (option c) is the best method.

Step 1: Analyzing the given options

We need to identify the most effective way to differentiate between the oxidation states of iron and nitrogen (as NO and NO+) in the nitroprusside ion. Let's analyze what is required for each option.

Step 2: Understanding Option A

Estimating the concentration of iron (option a) involves determining the amount of iron present in a sample. This technique would not directly show whether the iron is in the +2 or +3 oxidation state.

Step 3: Understanding Option B

Measuring the concentration of CN (option b) involves analyzing the cyanide ion concentration. This measurement would not provide information regarding the oxidation states of iron or NO.

Step 4: Review of Solid State Magnetic Moment—Option C

Measuring the solid state magnetic moment (option c) involves detecting the magnetic properties associated with unpaired electrons. The oxidation state of iron in the nitroprusside ion would influence the magnetic moment due to the change in electron configuration.

Step 5: Understanding Option D—Thermal Decomposition

Thermally decomposing the compound (option d) might break down the compound's structure, but it would not directly indicate the oxidation states of the individual elements prior to decomposition.

Step 6: Conclusion on Best Option

Measuring the solid state magnetic moment (option c) is the best way to distinguish the presence of iron in its different oxidation states because it is sensitive to changes in electron configuration, indicative of Fe in different oxidation states and NO+/NO variations.

Key Concepts

Oxidation States

Oxidation states are a way to keep track of electrons in chemical reactions, especially when dealing with coordination compounds like the nitroprusside ion. In chemistry, the oxidation state of an element is an indicator of the degree of oxidation (or loss of electrons) that the element has undergone.

• Oxidation is the process where an atom, ion, or molecule loses electrons.
• Reduction is the process where an atom, ion, or molecule gains electrons.
• In coordination compounds, metals like iron often exist in multiple oxidation states, affecting their chemical behavior.

In the nitroprusside ion, for example, iron can exist as either \(\mathrm{Fe}^{\mathrm{II}}\) or \(\mathrm{Fe}^{\mathrm{III}}\), depending on electron loss. Understanding oxidation states is essential for predicting reactivity and bonding characteristics.
The oxidation state of iron in the nitroprusside ion, where it exists as \(\mathrm{Fe}^{\mathrm{II}}\), is crucial to its role in the compound, influencing its magnetic and optical properties. This affects how it interacts with other substances and how it can be detected or analyzed in a lab setting.

Magnetic Moment

Magnetic moment is a measure of the magnetic strength and orientation of a magnet or other object that produces a magnetic field. In chemistry, this is particularly important for understanding the properties of transition metals like iron.

• The magnetic moment arises from electron spin and orbital motion.
• Unpaired electrons in an atom contribute to a larger magnetic moment.
• By measuring the magnetic moment, chemists can infer details about the electron configuration of a metal ion.

In the context of the nitroprusside ion, measuring the solid-state magnetic moment can give clues about the oxidation state of iron. When iron exists in a lower oxidation state like \(\mathrm{Fe}^{\mathrm{II}}\), it typically has more unpaired electrons compared to when it is in a higher oxidation state such as \(\mathrm{Fe}^{\mathrm{III}}\). Thus, a change in magnetic moment can suggest a change in oxidation state. This is why measuring the magnetic properties of the nitroprusside ion could be an effective way to differentiate between the oxidation states present.

Nitroprusside Ion

The nitroprusside ion is a fascinating example of a coordination compound consisting of the \(\mathrm{Fe(CN)_5NO}\) complex. It contains iron and nitrosyl (NO), which are part of its core structure and the source of its unique properties.

• The iron is typically in the +2 oxidation state when combined with NO⁺.
• The nitrosyl unit can exist in different forms, most commonly NO or NO⁺.
• These oxidation forms impact the compound's color, magnetic properties, and reactivity.

The nitroprusside ion is known for its intense red color in aqueous solutions, which is due to electron transitions within the ion. It is also an important molecule in medical diagnostics, especially as a reagent for detecting certain ions in bodily fluids. When working with the nitroprusside ion, understanding the relationship between the iron and NO⁺, the role of their respective oxidation states, and their impact on the compound's behavior is crucial. Such knowledge helps predict how the ion will react under different chemical conditions, providing insights useful in both laboratory analysis and practical applications.