Problem 62 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

In nitroprusside ion the iron and NO exist as \(\mathrm{Fe}^{\mathrm{II}}\) and \(\mathrm{NO}^{+}\)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 problem asks which method would best differentiate between two different electronic states of iron and NO in the nitroprusside ion: \(\text{Fe}^{\text{II}}\) and \(\text{NO}^{+}\) vs. \(\text{Fe}^{\text{III}}\) and NO.

Step 2: Analyzing Option (a)

Estimating the concentration of iron does not directly indicate the oxidation state of iron (\(\text{Fe}^{\text{II}}\) vs \(\text{Fe}^{\text{III}}\)). It only provides the total amount of iron present.

Step 3: Analyzing Option (b)

Measuring the concentration of \(\text{CN}^{-}\) does not give information about the oxidation states of iron or NO in the complex.

Step 4: Analyzing Option (c)

Measuring the solid state magnetic moment can provide insight into the electronic configuration of metal ions. \(\text{Fe}^{\text{II}}\) will have a different magnetic moment compared to \(\text{Fe}^{\text{III}}\) due to the difference in the number of unpaired electrons.

Step 5: Analyzing Option (d)

Thermally decomposing the compound will break it down, possibly making it harder to study the differing forms of \(\text{Fe}^{\text{II}}\) and NO vs. \(\text{Fe}^{\text{III}}\) and NO.

Step 6: Choosing the Best Method

Option (c), measuring the solid state magnetic moment, is the best method to differentiate between \(\text{Fe}^{\text{II}}\) and \(\text{Fe}^{\text{III}}\) because it directly relates to the electronic configuration and magnetic properties, which vary between these oxidation states.

Key Concepts

Oxidation States

The nitroprusside ion is an interesting compound where understanding oxidation states is crucial. Oxidation state refers to the total number of electrons that an atom either gains or loses to form a chemical bond. In the nitroprusside ion, we are concerned with distinguishing between

• \( ext{Fe}^{ ext{II}}\), which means iron has lost 2 electrons, and
• \( ext{Fe}^{ ext{III}}\), where iron has lost 3 electrons.

Both scenarios present different chemical properties.

Moreover, nitrogen in NO can also have varying oxidation states,

• In \( ext{NO}^{+}\), nitrogen loses one more electron, making it different from neutral NO.

These differences in oxidation states are significant as they affect how we predict reactivity and interact within the compound, helping us solve chemical equations more accurately.

Magnetic Moment

The magnetic moment is primarily determined by the number of unpaired electrons in a material. In the context of the nitroprusside ion, this property helps differentiate between \( ext{Fe}^{ ext{II}}\) and \( ext{Fe}^{ ext{III}}\). Electronic configurations influence magnetic behaviors in the following way:

• \( ext{Fe}^{ ext{II}}\) typically features more unpaired electrons, leading to a higher magnetic moment.
• \( ext{Fe}^{ ext{III}}\), on the other hand, often has a different count or arrangement of unpaired electrons, resulting in a different magnetic moment.

This distinction allows scientists to identify the oxidation state of iron through precise magnetic measurements. By measuring the magnetic moment in solid-state, we can determine whether we are dealing with \( ext{Fe}^{ ext{II}}\) or \( ext{Fe}^{ ext{III}}\), thus providing insight into the electronic configuration without altering the compound's structure.

Electronic Configuration

Electronic configuration involves the arrangement of electrons in an atom or molecule. It defines how electrons fill various available orbitals based on energy levels. In complex ions like nitroprusside, electronic configuration can offer clues about magnetic moments and chemical properties:

• For \( ext{Fe}^{ ext{II}}\), you will typically find a configuration like \([Ar] 3d^6 4s^0\), indicating unpaired electrons which contribute to its magnetism.
• In contrast, \( ext{Fe}^{ ext{III}}\) might have a configuration of \([Ar] 3d^5 4s^0\), featuring a different splitting pattern in its d-orbitals.

Understanding these configurations is essential for predicting how ions such as \( ext{Fe}^{ ext{II}}\) and \( ext{Fe}^{ ext{III}}\) behave chemically and physically, affecting their coordination environment and reactivity in chemical processes.