Question

Extra pure \(\mathrm{N}_{2}\) can be obtained by heating (A) \(\mathrm{NH}_{3}\) with \(\mathrm{CuO}\) (B) \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) (C) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) (D) \(\mathrm{Ba}\left(\mathrm{N}_{3}\right)_{2}\)

Short answer

Extra pure \(\mathrm{N}_{2}\) can be obtained by heating option (A) \(\mathrm{NH}_{3}\) with \(\mathrm{CuO}\).

Step-by-step solution

Understand the decomposition reactions

Each reactant listed decomposes upon heating to produce various products. Determine the chemical equation for the decomposition of each compound.

Write the balanced chemical equations

The balanced chemical equations for the decomposition of each compound are:(A) \(2\mathrm{NH}_{3} + 3\mathrm{CuO} \rightarrow N_{2} + 3\mathrm{Cu} + 3\mathrm{H}_{2}O\) (produces nitrogen)(B) \(\mathrm{NH}_{4}\mathrm{NO}_{3} \rightarrow N_{2}O + 2\mathrm{H}_{2}O\) (does not produce nitrogen)(C) \((\mathrm{NH}_{4})_{2}\mathrm{Cr}_{2}\mathrm{O}_{7} \rightarrow \mathrm{Cr}_{2}\mathrm{O}_{3} + N_{2} + 4\mathrm{H}_{2}O\) (produces nitrogen)(D) \(\mathrm{Ba}(\mathrm{N}_{3})_{2} \rightarrow \mathrm{Ba}\mathrm{N}_{2} + 3N_{2}\) (produces nitrogen)

Identify the correct option

The compounds that decompose to produce extra pure \(N_{2}\) are those whose decomposition reaction directly yields \(N_{2}\) without any other nitrogenous compounds. For this, options (A), (C), and (D) are valid. However, extra pure \(N_{2}\) is most likely to be obtained from option (A) as it has no other gaseous byproducts except \(N_{2}\).

Key concepts

Chemical Decomposition Reactions

Chemical decomposition reactions are a subclass of chemical reactions where a single compound breaks down into two or more elements or new compounds. These reactions typically require energy input, often in the form of heat, to break the chemical bonds of the reactant. For instance, when we apply heat to ammonium dichromate \( (\mathrm{NH}_4)_2\mathrm{Cr}_2\mathrm{O}_7 \), it decomposes into chromium oxide \( \mathrm{Cr}_2\mathrm{O}_3 \), nitrogen gas \( N_2 \), and water vapor. This type of reaction is represented by a general equation:

\( \mathrm{AB} \rightarrow \mathrm{A} + \mathrm{B} \) or \( \mathrm{ABC} \rightarrow \mathrm{A} + \mathrm{BC} \).

• In the context of generating pure nitrogen, we look for a decomposition that results in nitrogen gas as one of the products.
• Understanding the reactant and the conditions required for it to decompose is critical in predicting the products.
• Decomposition reactions are extensively used in industrial processes such as the production of cement and metals, and also in the preparation of various gases.

Balanced Chemical Equations

A balanced chemical equation is crucial for understanding the stoichiometry of a chemical reaction, ensuring that the law of conservation of mass is upheld. In other words, there should be an equal number of each type of atom on both sides of the reaction equation.

When writing balanced chemical equations, one must:

• Count the number of atoms of each element on both sides of the reaction.
• Adjust coefficients (the numbers before the chemical formulas) as necessary to achieve balance.
• Remember that the coefficients represent the relative amounts of moles of each substance involved in the reaction.

In our nitrogen generation example:

\(2\mathrm{NH}_{3} + 3\mathrm{CuO} \rightarrow N_{2} + 3\mathrm{Cu} + 3\mathrm{H}_{2}O \) shows a balanced decomposition reaction. We verify this equation by ensuring the number of nitrogen, hydrogen, copper, and oxygen atoms are equal on both sides. It's important not to change the subscripts (the small numbers in the formulas), as this would alter the compounds themselves.

Inorganic Chemistry

Inorganic chemistry focuses on the properties and behaviors of inorganic compounds, which are often defined as substances not containing a carbon-hydrogen (C-H) bond, in contrast to organic compounds. Subfields within inorganic chemistry include the study of minerals, metals, salts, and gases.

Considering nitrogen generation:

Inorganic compounds are often used to produce gases industrially. The compounds in the original exercise \( \mathrm{NH}_{3}, \mathrm{NH}_{4}\mathrm{NO}_{3}, (\mathrm{NH}_{4})_{2}\mathrm{Cr}_{2}\mathrm{O}_{7}, \mathrm{Ba}(\mathrm{N}_{3})_{2} \) are all inorganic, and their decomposition reactions are studied within the realm of inorganic chemistry.

• Ammonia \( NH_3 \) is a simple inorganic compound that when heated with copper(II) oxide \( CuO \) can yield pure \(N_2\).
• The stability, reactivity, and decomposition of inorganic compounds are all critical for designing processes that yield desired products like pure nitrogen gas.
• The exercise highlights the application of inorganic chemistry concepts to practical problems, such as obtaining pure substances from complex compounds.