Problem 71 - A Complete Resource Book in Chemistry for JEE Main

Question

\(\mathrm{NH}_{3}\) cannot be obtained by (a) heating of \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) or \(\mathrm{NH}_{4} \mathrm{NO}_{2}\) (b) heating of \(\mathrm{NH}_{4} \mathrm{Cl}\) or \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}\) (c) heating of \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) with \(\mathrm{NaOH}\) (d) reaction of AIN or \(\mathrm{Mg}_{3} \mathrm{~N}_{2}\) or \(\mathrm{CaCN}_{2}\) with \(\mathrm{H}_{2} \mathrm{O}\)

Step-by-Step Solution

Answer

\(\mathrm{NH}_3\) cannot be obtained by heating of \(\mathrm{NH}_4\mathrm{NO}_3\) or \(\mathrm{NH}_4\mathrm{NO}_2\) (option a).

Step 1: Identify the reaction products of option (a)

Let's consider the compounds given in option (a): \(\mathrm{NH}_4\mathrm{NO}_3\) decomposes upon heating to produce \(\mathrm{N}_2\mathrm{O}\) and \(\mathrm{H}_2\mathrm{O}\), not \(\mathrm{NH}_3\). Similarly, \(\mathrm{NH}_4\mathrm{NO}_2\) decomposes to give \(\mathrm{N}_2\) and \(\mathrm{H}_2\mathrm{O}\). Hence, \(\mathrm{NH}_3\) is not formed in both cases.

Step 2: Check the reaction products of option (b)

Consider option (b), where \(\mathrm{NH}_4\mathrm{Cl}\) and \((\mathrm{NH}_4)_2\mathrm{CO}_3\) are heated. Both compounds decompose to release \(\mathrm{NH}_3\). Thus, \(\mathrm{NH}_3\) can be formed from these reactions.

Step 3: Analyze the reaction in option (c)

For option (c), when \(\mathrm{NH}_4\mathrm{NO}_3\) is treated with \(\mathrm{NaOH}\), the reaction produces \(\mathrm{NH}_3\), \(\mathrm{NaNO}_3\), and \(\mathrm{H}_2\mathrm{O}\). \(\mathrm{NH}_3\) is indeed formed here.

Step 4: Evaluate the reaction conditions for option (d)

In option (d), \(\mathrm{NH}_3\) is obtained by the hydrolysis of compounds like \(\mathrm{AlN}\), \(\mathrm{Mg}_3\mathrm{N}_2\), and \(\mathrm{CaCN}_2\). All these compounds react with water to yield \(\mathrm{NH}_3\).

Key Concepts

Decomposition Reactions

Decomposition reactions are chemical reactions where a compound breaks down into simpler substances. These reactions generally involve the breakdown of a compound into two or more components. The process often requires an external source of energy, such as heat. During heating, some ammonium compounds decompose by losing nitrogen or oxygen atoms.

For instance, when you heat ammonium nitrate (otext{NH}_4 ext{NO}_3) it breaks down to produce dinitrogen monoxide (otext{N}_2 ext{O}) and water (otext{H}_2 ext{O}). Similarly, ammonium nitrite (otext{NH}_4 ext{NO}_2) decomposes to form nitrogen gas (otext{N}_2) and water. Notice how ammonia (otext{NH}_3) is absent in the products of these decompositions.

• Ammonium nitrate: \[ ext{NH}_4 ext{NO}_3 ightarrow ext{N}_2 ext{O} + ext{H}_2 ext{O}\]
• Ammonium nitrite: \[ ext{NH}_4 ext{NO}_2 ightarrow ext{N}_2 + ext{H}_2 ext{O}\]

Understanding these principles can help in predicting the products of similar reactions.

Ammonium Compounds

Ammonium compounds are chemical compounds that contain the ammonium ion (otext{NH}_4^+). Common examples include ammonium chloride (otext{NH}_4 ext{Cl}) and ammonium carbonate (( ext{NH}_4)_2 ext{CO}_3), both of which play important roles in producing ammonia through heating.

When heated, ammonium chloride decomposes into ammonia and hydrogen chloride (otext{HCl}), while ammonium carbonate releases ammonia. This makes them suitable sources for generating ammonia in controlled environments.

• Ammonium chloride: \[ ext{NH}_4 ext{Cl} ightarrow ext{NH}_3 + ext{HCl}\]
• Ammonium carbonate: \[( ext{NH}_4)_2 ext{CO}_3 ightarrow ext{NH}_3 + ext{CO}_2 + ext{H}_2 ext{O}\]

The availability of ammonia from these compounds under the right conditions illustrates their functional versatility.

Chemical Reactions Analysis

Chemical reaction analysis involves understanding the transformations that substances undergo during chemical reactions. In analyzing reactions, one focuses on reactants and products, identifying what new substances are formed. This process is crucial in predicting products like ammonia in certain reactions.

Let's consider the decomposition of ammonium nitrate (otext{NH}_4 ext{NO}_3) with sodium hydroxide (otext{NaOH}). When these compounds are combined, a chemical reaction takes place forming ammonia (otext{NH}_3), sodium nitrate (otext{NaNO}_3), and water.

• Ammonium nitrate with sodium hydroxide: \[ ext{NH}_4 ext{NO}_3 + ext{NaOH} ightarrow ext{NH}_3 + ext{NaNO}_3 + ext{H}_2 ext{O}\]

In this instance, analyzing the reaction indicates the formation of ammonia. Similarly, reactions of aluminum nitride (otext{AlN}), magnesium nitride (otext{Mg}_3 ext{N}_2) and calcium cyanamide (otext{CaCN}_2) with water also yield ammonia by examining their respective transformations.

Through analyzing chemical reactions, we can better predict outcomes and understand the practical applications of these reactions in ammonia production.