Question

Ammonium compound which does not give \(\mathrm{NH}_{3}\) on heating is (a) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\) (b) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}\) (c) \(\mathrm{NH}_{4} \mathrm{NO}_{2}\) (d) \(\mathrm{NH}_{4} \mathrm{Cl}\)

Short answer

The ammonium compound that does not give \(\mathrm{NH}_3\) upon heating is \(\mathrm{NH}_4 \mathrm{NO}_2\) (option c).

Step-by-step solution

Identify Ammonium Compounds

List down each of the given ammonium compounds and remember that they contain ammonium ion (\(\mathrm{NH}_4^+\)) bonded to different anions.

Determine Possible Reactions on Heating

Consider what happens to each compound when heated. Most ammonium compounds decompose to release ammonia gas (\(\mathrm{NH}_3\)). Determine what gases each compound releases upon decomposition.

Analyze Decomposition of Each Compound

(a) \((\mathrm{NH}_4)_2 \mathrm{SO}_4\) decomposes to release \(\mathrm{NH}_3\).(b) \((\mathrm{NH}_4)_2 \mathrm{CO}_3\) releases \(\mathrm{NH}_3\) upon heating.(c) \(\mathrm{NH}_4 \mathrm{NO}_2\) decomposes to form nitrogen gas (\(\mathrm{N}_2\)) and water, not \(\mathrm{NH}_3\).(d) \(\mathrm{NH}_4 \mathrm{Cl}\) releases \(\mathrm{NH}_3\) and \(\mathrm{HCl}\) gas when heated.

Identify Exception

Find the compound that does not produce \(\mathrm{NH}_3\) gas upon heating. From the above analysis, recognize that \(\mathrm{NH}_4 \mathrm{NO}_2\) is the exception as it decomposes directly into \(\mathrm{N}_2\) and water.

Key concepts

Ammonium Ion

The ammonium ion, denoted by the formula \( \mathrm{NH}_4^+ \), is a positively charged ion. It's a familiar player in chemistry, especially in the realm of ionic compounds. This ion comes from ammonia \((\mathrm{NH}_3)\) by adding one more hydrogen ion \((\mathrm{H}^+)\). Its presence is quite common in ammonium salts, where it pairs up with a negative ion, known as an anion.

Ammonium ions are versatile. They easily form compounds with various anions, resulting in different ammonium compounds like ammonium sulfate \((\mathrm{NH}_4)_2 \mathrm{SO}_4\), ammonium carbonate \((\mathrm{NH}_4)_2 \mathrm{CO}_3\), or ammonium chloride \(\mathrm{NH}_4 \mathrm{Cl}\). Amit is essential to note that the ammonium ion is fundamental in the nitrogen cycle, playing a crucial role in plant nutrition as well.

When it comes to heating these compounds, interesting reactions happen due to the behavior of the ammonium ion. Understanding these reactions is key to solving problems related to ammonium compounds and their thermal stability.

Decomposition Reactions

Decomposition reactions are fascinating chemical processes where a single compound breaks down into two or more simpler substances. This process is vital in various chemical and industrial processes.

In the context of ammonium compounds, many undergo decomposition when heated. This is typically represented by the breakdown of the compound into gases like ammonia \((\mathrm{NH}_3)\) or other substances, depending on the specific anion involved.

The chemical reaction of decomposition often includes these phases:

• Ammonium sulfate \((\mathrm{NH}_4)_2 \mathrm{SO}_4\) decomposes to release ammonia.
• Ammonium carbonate \((\mathrm{NH}_4)_2 \mathrm{CO}_3\) decomposes into ammonia and carbon dioxide.
• Uniquely, ammonium nitrite \((\mathrm{NH}_4 \mathrm{NO}_2)\) breaks down directly into nitrogen gas \((\mathrm{N}_2)\) and water without releasing ammonia.
• Ammonium chloride \(\mathrm{NH}_4 \mathrm{Cl}\) liberates ammonia and hydrochloric acid \(\mathrm{HCl}\) gases.

Understanding these reactions gives insight into predicting the behavior of ammonium compounds under heat, and allows for solving related chemical problems with ease.

Gas Evolution

In chemistry, gas evolution is a process where gases are produced during chemical reactions. It's a key consideration, especially when dealing with decomposition reactions involving ammonium compounds.

When an ammonium compound undergoes decomposition due to heating, the result is often the evolution of gases. This can include:

• Release of ammonia \((\mathrm{NH}_3)\) gas in most cases.
• Unique production of nitrogen gas \((\mathrm{N}_2)\) in the decomposition of ammonium nitrite \((\mathrm{NH}_4 \mathrm{NO}_2)\).
• In some reactions, like with ammonium chloride \(\mathrm{NH}_4 \mathrm{Cl}\), evolution of both ammonia and hydrochloric acid \((\mathrm{HCl})\) gases.

Gas evolution is pivotal in identifying the nature of a decomposition reaction and the specific gases liberated can help distinguish between different ammonium compounds when heated.

Having a firm grasp on this concept is instrumental for understanding chemical processes and in making accurate predictions in chemical experiments and applications. It's like solving a puzzle, where each evolved gas represents a clue in the decomposition mystery.