Problem 133 - A Complete Resource Book in Chemistry for JEE Main

Question

Nitrogen is prepared by heating (a) Microcosmic salt, \(\mathrm{NaNH}_{4} \mathrm{HPO}_{4} \cdot 4 \mathrm{H}_{2} \mathrm{O}\) (b) A mixture of \(\mathrm{CuO}\) and \(\mathrm{NH}_{3}\) (c) A mixture of \(\mathrm{NH}_{4} \mathrm{Cl}\) and \(\mathrm{NaNO}_{3}\) (d) Barium azide

Step-by-Step Solution

Answer

Nitrogen is prepared by heating (b), (c), or (d).

Step 1: Identify the Reaction

To find out how nitrogen is prepared from the given substances, we need to look at the reactions involving these compounds. Nitrogen gas (\(N_2\)) can be produced from several chemical processes depending on the reactants involved.

Step 2: Analyze Option (a)

Heating microcosmic salt (\(\mathrm{NaNH}_{4} \mathrm{HPO}_{4} \cdot 4 \mathrm{H}_{2} \mathrm{O}\)) leads to the formation of complex phosphorus and sodium-derived compounds, but it does not produce nitrogen gas. Thus, option (a) is not the correct method for preparing nitrogen.

Step 3: Analyze Option (b)

The reaction between \(\mathrm{CuO}\) and \(\mathrm{NH}_3\) when heated involves \(\mathrm{NH}_3\) being oxidized to produce \(\mathrm{N}_2\) and \(\mathrm{H}_2\mathrm{O}\). This provides a means to generate nitrogen. The reaction is: \(\mathrm{3CuO} + 2\mathrm{NH}_3 \rightarrow 3\mathrm{Cu} + \mathrm{N}_2 + 3\mathrm{H}_2\mathrm{O}\). Thus, option (b) is a valid method.

Step 4: Analyze Option (c)

When \(\mathrm{NH}_4\mathrm{Cl}\) and \(\mathrm{NaNO}_3\) are heated together, they undergo a reaction to form \(\mathrm{N}_2\), \(\mathrm{NaCl}\), and \(\mathrm{H}_2\mathrm{O}\). The balanced reaction is: \(\mathrm{NH}_4\mathrm{Cl} + \mathrm{NaNO}_3 \rightarrow \mathrm{N}_2 + \mathrm{NaCl} + 2\mathrm{H}_2\mathrm{O}\). Thus, option (c) is also a valid method.

Step 5: Analyze Option (d)

Barium azide (\(\mathrm{Ba(N}_3\mathrm{)_2}\)) upon heating decomposes into barium and nitrogen gas. The reaction is: \(\mathrm{Ba}{(\mathrm{N}_3)}_2 \rightarrow \mathrm{Ba} + 3\mathrm{N}_2\). Hence, option (d) is also a valid method to produce nitrogen.

Step 6: Conclusion

After examining all the options, it is evident that options (b), (c), and (d) can be used to prepare nitrogen gas by heating.

Key Concepts

Chemical Reactions

Chemical reactions play a crucial role in transforming substances into different chemical structures. In the context of nitrogen preparation, various chemical reactions are employed to generate nitrogen gas rom different compounds. Each reaction involves breaking chemical bonds in the reactants and forming new ones to produce products.
Let's delve into some examples:

• When heating a mixture of CuO and NH extsubscript{3}, ammonia is oxidized to produce nitrogen gas, copper, and water.
• Heating a combination of NH extsubscript{4}Cl and NaNO extsubscript{3} results in the production of N extsubscript{2}, NaCl, and water.
• Barium azide, when heated, decomposes into barium and nitrogen gas.

Chemical reactions are governed by a set of rules known as stoichiometry, which ensures that the number of atoms within reactants is conserved in the products. Understanding these reactions enables us to efficiently produce nitrogen gas.

Nitrogen Gas Production

Nitrogen gas ( N extsubscript{2}) is a vital component of our atmosphere, making up about 78% of its composition. Despite this abundance, producing nitrogen in a controlled environment is essential to meet various industrial needs.
In laboratories and industries, controlled reactions are used to liberate nitrogen gas from specific compounds:

• Combinations of chemicals such as NH extsubscript{4}Cl and NaNO extsubscript{3} are heated to generate N extsubscript{2} in a controlled setup.
• Other sources like barium azide cost-effectively provide pure nitrogen upon decomposition.

Industrially, nitrogen gas is produced through methods like fractional distillation of liquefied air, but these chemical reactions provide a straightforward manner to produce smaller batches of nitrogen for specific applications.

Heating Reactions

The process of heating compounds can drive chemical reactions that wouldn't occur at lower temperatures. Heat provides energy to break the bonds of reacting substances, allowing new bonds and thus new products to form.
When it comes to preparing nitrogen, heating is an essential part of the process:

• The reaction between CuO and NH extsubscript{3} only takes place when heated, allowing the production of nitrogen gas.
• Similarly, heating NH extsubscript{4}Cl with NaNO extsubscript{3} or barium azide initiates the necessary transformations to release nitrogen.

Understanding how heat influences these reactions helps in making efficient use of materials to produce desired outputs. It also emphasizes the importance of controlled heating in generating pure substances.