Problem 73 - A Complete Resource Book in Chemistry for JEE Main

Question

Ammonia reacts with sodium hypochlorite to give (a) \(\mathrm{N}_{2} \mathrm{O}\) (b) \(\mathrm{N}_{2}\) (c) \(\mathrm{NH}_{2} \mathrm{OH}\) (d) \(\mathrm{H}_{2} \mathrm{~N} . \mathrm{NH}_{2}\)

Step-by-Step Solution

Answer

The reaction of ammonia with sodium hypochlorite gives (b) \(\mathrm{N}_2\).

Step 1: Understand the Reaction

Ammonia (\(\mathrm{NH_3}\)) is reacting with sodium hypochlorite (\(\mathrm{NaOCl}\)). This type of reaction involves the swapping of elements between the substances, known as a redox reaction.

Step 2: Determine Possible Products

When ammonia reacts with sodium hypochlorite, common nitrogen-containing products include hydrazine (\(\mathrm{N_2H_4}\)), nitrogen gas (\(\mathrm{N_2}\)), and nitrous oxide (\(\mathrm{N_2O}\)). We need to determine which one is formed under typical conditions.

Step 3: Evaluate the Choices

The options include \(\mathrm{N}_2\mathrm{O}\), \(\mathrm{N}_2\), \(\mathrm{NH}_2\mathrm{OH}\), and diazene (\(\mathrm{H}_2\mathrm{N.NH}_2\)). Considering the typical conditions for this reaction, nitrogen gas (\(\mathrm{N_2}\)) is often formed as the final product when ammonia and sodium hypochlorite react.

Step 4: Confirm Reaction Environment

Ammonia typically reacts with sodium hypochlorite at higher temperatures, resulting in the formation of nitrogen gas. This confirms that \(\mathrm{N_2}\) is the likely product formed under these conditions.

Key Concepts

Redox Reaction

Redox reactions, short for reduction-oxidation reactions, are a fascinating category of chemical reactions. They involve the transfer of electrons between two substances, leading to a change in their oxidation states. In a redox reaction, one substance loses electrons (is oxidized), while another gains electrons (is reduced).
When ammonia ( H_3 ext{) reacts with sodium hypochlorite ( NaOCl ext{), a redox reaction occurs. In this particular chemical reaction:

• Ammonia serves as the reducing agent, which means it donates electrons.
• Sodium hypochlorite acts as the oxidizing agent, accepting electrons.

This exchange alters the oxidation states of nitrogen and chlorine, playing a crucial role in forming various nitrogen-based products, such as nitrogen gas or hydrazine.

Nitrogen Gas

Nitrogen gas ( N_2 ext{) is a diatomic molecule composed of two nitrogen atoms. It is one of the most abundant and stable gases in Earth's atmosphere.
In the reaction between ammonia and sodium hypochlorite, nitrogen gas is a potential product. The stability and inert nature of N_2 ext{ make it a favored product under typical reaction conditions.
When assessing reactions such as the ammonia-sodium hypochlorite reaction:

• Nitrogen gas forms as the result of breaking and reforming bonds between nitrogen atoms.
• This gas is notable for its lack of reactivity, contributing to why it's often the final product.

Its formation simplifies the reaction process and is generally favored at higher temperatures.

Hydrazine

Hydrazine ( N_2H_4 ext{) is a nitrogen-rich compound that results from reactions involving ammonia and oxidizing agents. It consists of two nitrogen atoms bonded together, along with additional hydrogen atoms.
In the context of ammonia reacting with sodium hypochlorite, hydrazine is one of the possible nitrogen-based products. It serves as an important intermediate:

• Hydrazine is known for its powerful reducing properties, which contribute to other chemical processes.
• It can further decompose to form other products like nitrogen gas, especially under varying temperature and pressure conditions.

Despite its potential formation, hydrazine is generally not the primary product under typical conditions in this reaction context.

Typical Reaction Conditions

Typical conditions for the ammonia and sodium hypochlorite reaction play a vital role in determining the products formed. Under normal laboratory settings:

• The reaction is often conducted at elevated temperatures, which influences the dominance of particular reaction pathways.
• Higher temperatures facilitate the breakdown of intermediates into more stable products, such as nitrogen gas ( N_2 ext{).

Moreover, understanding the environment is key:

• The concentration of reactants, temperature, and pressure all affect which nitrogen compound becomes the final product.
• Careful control of these conditions can optimize the production of desired products or minimize unwanted by-products.

Each variable in these typical conditions contributes significantly to the chemical dynamics and outcome of the ammonia-sodium hypochlorite reaction.