Problem 67 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is a nitric acid anhydride? (a) \(\mathrm{N}_{2} \mathrm{O}_{5}\) (b) NO (c) \(\mathrm{NO}_{2}\) (d) \(\mathrm{N}_{2} \mathrm{O}_{3}\)

Step-by-Step Solution

Answer

The nitric acid anhydride is N₂O₅ (option a).

Step 1: Definition of Anhydride

An anhydride is a compound formed by removing water (H₂O) from an acid. In the context of nitric acid (HNO₃), a nitric acid anhydride would be a compound formed by removing water from this acid.

Step 2: Formula for Nitric Acid

The chemical formula for nitric acid is HNO₃. To form an anhydride from HNO₃, we need to look for a compound derived by removing H₂O from its molecular structure.

Step 3: Deriving the Anhydride

The conversion from HNO₃ to its anhydride involves 2 molecules of HNO₃ losing a water molecule, leading to the formation of N₂O₅ based on the reaction: \( 2~ ext{HNO}_3 ightarrow ext{N}_2 ext{O}_5 + ext{H}_2 ext{O} \) .

Step 4: Compare Options

Given the options, N₂O₅ is the compound that matches the expected formula of a nitric acid anhydride obtained by removing water as shown in Step 3.

Key Concepts

Anhydrides

Anhydrides are fascinating compounds formed by removing water from other compounds, most commonly acids. When you hear the term "anhydride," think of a substance that lacks water.
This unique formation process gives anhydrides distinctive properties and uses in chemical reactions.

In the case of nitric acid, for example, its anhydride is created by removing one molecule of water from two molecules of nitric acid (HNO₃). The equation illustrating this transformation is: \[ 2~\text{HNO}_3 \rightarrow \text{N}_2\text{O}_5 + \text{H}_2\text{O} \]

• Anhydrides typically react with water to regenerate the original acid. So, if you add water back to an anhydride like \(\text{N}_2\text{O}_5\), it forms nitric acid.
  
• They're often used in organic synthesis and can act as dehydrating agents.

Understanding anhydrides sheds light on many chemical processes, especially in synthesis and industrial applications.

Chemical Reactions

Chemical reactions are transformations where substances, known as reactants, are converted to different substances called products. Every change involves breaking and forming bonds, which is fundamental to chemistry.
Let's consider the formation of nitric acid anhydride, as discussed in the exercise: \[ 2~\text{HNO}_3 \rightarrow \text{N}_2\text{O}_5 + \text{H}_2\text{O} \] This reaction illustrates how two nitric acid molecules lose a water molecule to produce an anhydride.

Key points about this chemical reaction include:

• It is a dehydration reaction, where water is removed.
  
• It happens because of the arrangement of atoms, resulting in a stable product in this case \(\text{N}_2\text{O}_5\).

Chemical reactions like these constantly occur around and within us, allowing for the myriad of processes necessary for life and technology.

Inorganic Chemistry

Inorganic chemistry is the branch of chemistry that deals with inorganic compounds, typically those not involving carbon-hydrogen bonds. This field encompasses a wide array of materials and processes, including the study of anhydrides like \(\text{N}_2\text{O}_5\).

Inorganic substances have critical applications in various industries:

• Anhydrides are prominent in the preparation of fertilizers, explosives, and in synthesis.
  
• The study of nitrogen-containing compounds, such as nitric acid and its anhydride, plays a critical role in industrial processes.

Inorganic chemistry provides insight into the behavior, structure, and reactivity of such compounds, offering a basis for technological advancements. Understanding this area better equips us to manipulate and utilize materials in beneficial ways.