Problem 58 - A Complete Resource Book in Chemistry for JEE Main

Question

Nitrogen is liberated by the thermal decomposition of only (a) \(\mathrm{NH}_{4} \mathrm{NO}_{2}\) (b) \(\mathrm{NaN}_{3}\) (c) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) (d) all the three

Step-by-Step Solution

Answer

(d) all the three

Step 1: Understand the Problem

We need to identify which compound(s) decompose upon heating to release nitrogen gas. Each given compound should be analyzed to determine the products of their thermal decomposition.

Step 2: Analyze Decomposition of NH4NO2

When ammonium nitrite ( ext{NH}_4 ext{NO}_2) is heated, it decomposes into nitrogen gas and water through the reaction: \[ ext{NH}_4 ext{NO}_2 ightarrow ext{N}_2 + 2 ext{H}_2 ext{O}\]Thus, nitrogen gas is liberated.

Step 3: Analyze Decomposition of NaN3

Sodium azide ( ext{NaN}_3) decomposes when heated to produce nitrogen gas and sodium through the reaction:\[2 ext{NaN}_3 ightarrow 2 ext{Na} + 3 ext{N}_2\]Therefore, nitrogen gas is liberated.

Step 4: Analyze Decomposition of (NH4)2Cr2O7

When ammonium dichromate (( ext{NH}_4)_2 ext{Cr}_2 ext{O}_7) decomposes upon heating, it releases nitrogen gas, water vapor, and chromium(III) oxide. The reaction is:\[( ext{NH}_4)_2 ext{Cr}_2 ext{O}_7 ightarrow ext{N}_2 + 4 ext{H}_2 ext{O} + ext{Cr}_2 ext{O}_3\]Thus, nitrogen gas is liberated.

Step 5: Conclusion

All three compounds ( ext{NH}_4 ext{NO}_2,  ext{NaN}_3, and ( ext{NH}_4)_2 ext{Cr}_2 ext{O}_7) release nitrogen gas on thermal decomposition.

Key Concepts

Nitrogen Gas Liberation

Thermal decomposition is a fascinating chemical process where compounds break down due to heat. When discussing nitrogen gas liberation, we refer to the release of nitrogen gas (_2) as a product of this decomposition. In many chemical reactions, heat acts as a catalyst that facilitates the breaking of bonds within a compound, resulting in smaller and more stable molecules.
- Ammonium nitrite (H_4O_2) decomposes into nitrogen gas and water.- Sodium azide (_3) breaks down to produce nitrogen gas and sodium.- Ammonium dichromate (\(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\)) releases nitrogen gas, water, and chromium(III) oxide upon heating.
Each of these reactions involves a transition where the compound splits into different substances, illustrating the beauty of chemical transformations. Understanding nitrogen gas liberation helps in better grasping how energy dynamics and stability drive chemical changes.

Chemical Reactions

Chemical reactions are transformations where substances known as reactants are converted to different substances called products. These transformations may involve changes in energy, where either energy is released or absorbed.
Thermal decomposition is a specific type of chemical reaction where heat causes the breakdown of compounds into simpler molecules. During this process, the energy supplied by heat helps to- Break existing chemical bonds in the reactants.- Form new bonds in the resultant products.
In the textbook problems,- \H_4\O_2 breaks into nitrogen gas and water.- 2\_3 decomposes into sodium and nitrogen gas.- \((\mathrm{NH}_4)_2\mathrm{Cr}_2\mathrm{O}_7\) yields nitrogen gas, water vapor, and chromium(III) oxide.
Each reaction highlights distinct pathways for decompositions, showcasing the role heat plays in transforming compounds. Observing these reactions in the lab can offer tangible insights into theoretical chemistry concepts.

Compounds Analysis

Analyzing chemical compounds involves understanding their composition and the potential reactions they undergo. It is crucial to determine what elements and bonds are present within a compound, as this determines how it will behave under specific conditions, such as exposure to heat in thermal decomposition.
For example, ammonium nitrite (H_4O_2) is examined by breaking it down to water and nitrogen gas upon heating. Similarly, sodium azide (_3) is scrutinized for its potential to produce sodium and nitrogen gas. Ammonium dichromate (\((\mathrm{NH}_4)_2\mathrm{Cr}_2\mathrm{O}_7\)) also illustrates how a complex compound can release nitrogen gas, alongside other byproducts.
By analyzing compounds, chemists design experiments and predict outcomes based on existing knowledge. Understanding a compound's structure allows us to foresee its interactions, making it a pivotal skill in the study of chemistry. This analysis aids in synthesizing new materials and predicting how compounds behave, enhancing the application of chemistry in everyday life.