Problem 92 - A Complete Resource Book in Chemistry for JEE Main

Question

Ammonia on reaction with hypochlorite anion can form (1) \(\mathrm{NO}\) (2) \(\mathrm{NH}_{4} \mathrm{Cl}\) (3) \(\mathrm{N}_{2} \mathrm{H}_{4}\) (4) \(\mathrm{HNO}_{2}\) (a) 1,2 (b) 2,3 (c) 3,4 (d) \(2,3,4\)

Step-by-Step Solution

Answer

(b) 2,3

Step 1: Understand the Reaction

Ammonia (NH₃) reacts with hypochlorite ion (OCl⁻) in a chemical reaction. This process involves chlorine compounds and nitrogen compounds, leading to various possible products.

Step 2: Potential Products of the Reaction

When ammonia reacts with hypochlorite ion, it can lead to several reactions: formation of monochloramine (NH₂Cl), dichloramine (NHCl₂), or nitrogen gas (N₂) and water, among others. Carefully consider the nitrogen-containing products mentioned in the options.

Step 3: Eliminate Improbable Products

Products like nitric oxide (NO) or nitrous acid ( HNO₂) are less commonly formed in these reactions because they typically emerge from oxidation reactions involving stronger oxidizing agents under specific conditions. Thus, options 1 and 4 are improbable immediate direct results of the NH₃ and OCl⁻ reaction.

Step 4: Identify Likely Combinations

Ammonium chloride (NH₄Cl) is a reasonable product as chlorine ions can combine with ammonium ions. Hydrazine (N₂H₄) can also form through reactions involving intermediate molecules of chloramines or oxidative reactions.

Step 5: Choose Correct Options

From the analysis, the correct set of products based directly on common reactions between ammonia and hypochlorite ion includes NH₄Cl and N₂H₄. Thus, the presented options that encompass these products are 2 and 3.

Key Concepts

Chloramine Formation

When ammonia \(\mathrm{NH}_3\) interacts with hypochlorite anion \(\mathrm{OCl^-}\), chloramines might form, which are nitrogen-chlorine compounds. Chloramines represent an intriguing group of temporary derivatives arising from the union of ammonia with chlorine sources.

• Monochloramine is \(\mathrm{NH}_2\mathrm{Cl}\)
• Dichloramine is \(\mathrm{NHCl}_2\)
• Trichloramine, which is more unstable and less common, is \(\mathrm{NCl}_3\)

Chloramines are often seen in water disinfection. Their formation through chlorine sources provides effective, albeit milder, antimicrobial activity compared to direct chlorination. This process prevents the formation of strict chlorine by-products.

Despite their use in sanitation, not all chloramines are equally desirable. At higher concentrations, especially dichloramine and trichloramine, can have irritating effects such as odor and adverse health effects. Chloramines involve careful balance and are critical to understanding reactions of ammonia with chlorine-based compounds.

Ammonium Chloride

Ammonium chloride (NH₄Cl) emerges from the combination of ammonia and hypochlorite under controlled conditions. This is because ammonia can accept a hydrogen ion to form the ammonium ion \(\mathrm{NH_4^+}\), which can then unite with chlorine ions to create ammonium chloride.In everyday scenarios:

• Ammonium chloride is used in fertilizers, as a nitrogen source.
• It's also found in cold packs, where its endothermic dissolution absorbs heat, bringing about a cooling effect.

Ammonium chloride's solubility in water and its acidic nature when dissolved also find applications in pharmaceuticals and as a flux in metalworking. When discussing ammonia reacting with chlorine-based compounds like hypochlorite, the formation of this salt becomes paramount.

Hydrazine Formation

The formation of hydrazine (N₂H₄) when ammonia reacts with hypochlorite is a fascinating display of chemical transformation. Hydrazine is an important compound in the aerospace and energy sectors because of its potential as a high-energy fuel due to its instability and ability to release substantial energy at combustion. In the presence of hypochlorite, several pathways can lead to hydrazine formation:

• Intermediates like chloramines can undergo further reactions.
• Hydrazine formation requires careful control as it hinges on intermediate reactions between ammonia derivatives and partially oxidized products.
• These intermediate reactions may involve steps where nitrogen atoms unite to form the longer N₂H₄ chain.

However, it's crucial to handle such reactions with care due to the instability of hydrazine, and it should never be allowed to accumulate in dangerous amounts. Despite its sensitivity, its formation marks a cornerstone in understanding ammonia and hypochlorite chemistry that can extend well beyond basic nitrogen-based products.