Problem 77 - A Complete Resource Book in Chemistry for JEE Main

Question

What are the products obtained when ammonia is reacted with excess chlorine? (a) \(\mathrm{N}_{2}\) and \(\mathrm{NH}_{4} \mathrm{Cl}\) (b) \(\mathrm{N}_{2}\) and \(\mathrm{NCl}_{3}\) (c) \(\mathrm{NCl}_{3}\) and \(\mathrm{HCl}\) (d) \(\mathrm{N}_{2}\) and \(\mathrm{HCl}\)

Step-by-Step Solution

Answer

The products are \(\text{N}_2\) and \(\text{HCl}\); correct answer is (d).

Step 1: Reaction of Ammonia with Limited Chlorine

When ammonia (\(\text{NH}_3\)) reacts with a limited amount of chlorine (\(\text{Cl}_2\)), nitrogen trichloride (\(\text{NCl}_3\)) and hydrogen chloride (\(\text{HCl}\)) are the main products, according to the reaction: \[ \text{NH}_3 + 3 \text{Cl}_2 \rightarrow \text{NCl}_3 + 3 \text{HCl}. \]

Step 2: Reaction of Ammonia with Excess Chlorine

With excess chlorine, the reaction proceeds further as \(\text{NCl}_3\) formed in the initial reaction is unstable and breaks down, forming nitrogen gas (\(\text{N}_2\)) and hydrogen chloride. The overall reaction is: \[ 8\text{NH}_3 + 3\text{Cl}_2 \rightarrow 6\text{N}_2 + 6\text{HCl} + 9\text{H}_2.\] But since \(\text{H}_2\) is seldom asked, it simplifies to nitrogen and HCl.

Step 3: Match with Given Options

Comparing the resulting products from the reaction (\(\text{N}_2\) and \(\text{HCl}\)) with the given options: Option (a): \(\text{N}_2\) and \(\text{NH}_4 \text{Cl}\)Option (b): \(\text{N}_2\) and \(\text{NCl}_3\)Option (c): \(\text{NCl}_3\) and \(\text{HCl}\)Option (d): \(\text{N}_2\) and \(\text{HCl}\).Option (d) matches the products.

Key Concepts

Understanding Nitrogen Gas

Nitrogen gas, commonly referred to as  ext{N}_2, is an inert, diatomic molecule. It is a major component of Earth's atmosphere, constituting about 78%. Because nitrogen is generally inert, it does not readily participate in chemical reactions. This property makes it valuable for creating inert atmospheres and preventing unwanted oxidation reactions.
Despite its inert nature, under certain conditions, nitrogen can form compounds. During chemical processes like the reaction of ammonia ( ext{NH}_3) with chlorine ( ext{Cl}_2), nitrogen gas is produced as one of the final products. In this reaction, the instability of intermediate compounds leads to the release of nitrogen gas.
This reaction serves as an example of how strategic manipulation of conditions can convert reactive gases into stable, inert nitrogen. This manipulation is important in industrial processes where control over reaction pathways is critical.

Exploring Hydrogen Chloride

Hydrogen chloride ( ext{HCl}) is a colorless gas with a sharp odor, often associated with hydrochloric acid when dissolved in water. It forms through various reactions, one of which involves the reaction between ammonia ( ext{NH}_3) and chlorine ( ext{Cl}_2).
The reaction of ammonia with chlorine not only produces nitrogen gas but also forms hydrogen chloride. This occurs when chlorine atoms displace hydrogen atoms in ammonia. The result is a product mixture containing  ext{HCl}.
Being a strong acid in aqueous solutions, hydrogen chloride is used extensively in the industry for producing chloride salts and purifying metals. Understanding the formation of hydrogen chloride allows students to comprehend how basic industrial chemicals are synthesized and utilized.

Insights into Nitrogen Trichloride

Nitrogen trichloride ( ext{NCl}_3) is a hazardous yellow oil and a by-product in various chemical reactions. It is formed when ammonia reacts with a limited supply of chlorine. Its formula shows three chlorine atoms attached to a single nitrogen atom.
However,  ext{NCl}_3 is highly unstable, especially in water, where it readily breaks down, releasing nitrogen gas and hydrogen chloride. This instability is crucial when dealing with the chemical, as it tends to decompose and sometimes even explode under the right conditions.
Despite its hazardous nature, understanding nitrogen trichloride is important, especially in the context of reactions like those compared in this exercise. Its propensity to form and then decompose highlights the complexities of chemical reactions and the importance of handling reactive intermediates safely.