Problem 134 - A Complete Resource Book in Chemistry for JEE Main

Question

Column-I (a) \(\mathrm{HNO}_{2}\) (aq) \(\longrightarrow\) (b) \(\mathrm{NH}_{4} \mathrm{Cl}\) (aq) \(+\mathrm{NaNO}_{2}\) (aq) \(\longrightarrow\) (c) \(\mathrm{HN}_{3}+\mathrm{Li} \longrightarrow\) (d) \(\mathrm{Mg}+\mathrm{HNO}_{3}\) (cold and dilute) \(\longrightarrow\) Column-II (p) One of the product is a diamagnetic colourless gas. (q) One of the products is a colourless paramagnetic gas. (r) Redox reaction (s) One of the products gives brown ring test.

Step-by-Step Solution

Answer

(a) -> (q), (b) -> (p), (c) -> (r), (d) -> (s).

Step 1: Analysis of Reaction (a)

The reaction involves the compound \(\mathrm{HNO}_{2}\), which can decompose to form a mixture of \(\mathrm{NO}\) gas and water. The resultant product \(\mathrm{NO}\) is a paramagnetic gas, matching with Column-II option (q).

Step 2: Analysis of Reaction (b)

The reaction between \(\mathrm{NH}_{4} \mathrm{Cl}\) and \(\mathrm{NaNO}_{2}\) leads to the formation of \(\mathrm{N}_{2}\) gas and other products. \(\mathrm{N}_{2}\) is a diamagnetic colorless gas, which corresponds to Column-II option (p).

Step 3: Analysis of Reaction (c)

The reaction of \(\mathrm{HN}_{3}\) with \(\mathrm{Li}\) involves a redox process. \(\mathrm{Li}\) reduces \(\mathrm{HN}_{3}\) to produce \(\mathrm{N}_{2}\) and \(\mathrm{LiN}_3\). Since it involves electron transfer, it is a redox reaction, which corresponds to Column-II option (r).

Step 4: Analysis of Reaction (d)

The reaction of \(\mathrm{Mg}\) with cold and dilute \(\mathrm{HNO}_{3}\) generates \(\mathrm{NO}\) and \(\mathrm{H_2O}\), among other products. \(\mathrm{NO}\) can react further in the environment to produce a compound that gives a brown ring test. This matches with Column-II option (s).

Key Concepts

Redox Reactions

One of the fundamental concepts in inorganic chemistry is the redox reaction, which stands for reduction-oxidation. In these reactions, electron transfer occurs between two substances. One substance loses electrons, known as oxidation, while the other gains electrons, which is called reduction.

• The substance that gives away electrons is known as the reducing agent because it reduces the other substance by donating electrons.
• Conversely, the substance gaining electrons is termed the oxidizing agent, as it oxidizes the other.

In reaction (c) from the exercise, lithium (Li) acts as a reducing agent as it donates electrons to azide ion ({HN}}_3), which results in the formation of nitrogen gas ({N}_2) and lithium azide ({LiN}_3). This exchange of electrons classifies it as a redox reaction, illustrating these two parallel processes, reduction and oxidation.

Gas Properties

The properties of gases such as being colorless or having magnetic characteristics can provide insight into compound identification during chemical reactions. Key terms related to gas properties include paramagnetism and diamagnetism. These properties are linked to electron configurations within the gas molecules.

• For example, in reaction (b), nitrogen gas (N}_2) forms, which is colorless and diamagnetic because its electrons are paired, leading to no net magnetic moment. The process reflects a situation where gases do not interact with magnetic fields.
• Similarly, in reaction (a), nitric oxide (NO) is a product that is paramagnetic due to unpaired electrons, which allows it to be influenced by a magnetic field.

These detailed characteristics allow chemists to predict the outcomes and behaviors of gases produced in chemical reactions.

Chemical Reactions Analysis

Analyzing chemical reactions is essential for understanding the intricate changes that substances undergo. It involves recognizing the reactants, predicting products, and interpreting reaction types, like redox reactions.

• In reaction (a) and (d), nitric oxide (NO) is produced. Proper analysis indicates NO as a paramagnetic molecule because it has an unpaired electron.
• Similarly, reaction (b) produces nitrogen (N_2), highlighting gas properties and showing it's diamagnetic due to paired electrons.

Such analysis in chemistry helps visualize and predict the transformations at the molecular level, which is crucial for solving problems related to reaction equations and product formation.

Paramagnetic and Diamagnetic Substances

Understanding the difference between paramagnetic and diamagnetic substances is crucial in inorganic chemistry, as it determines how these substances interact with external magnetic fields.

• Paramagnetic substances, like nitric oxide (NO) from reaction (a) and (d), have at least one unpaired electron, making them attracted to magnetic fields.
• On the other hand, diamagnetic substances, such as nitrogen gas ({N}_2) from reaction (b), have all their electrons paired, resulting in a repelling effect from magnetic fields.

Identifying whether a compound is paramagnetic or diamagnetic assists chemists in deducing molecular structures and properties, aiding in the synthesis and analysis of new substances in the chemical landscape.