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) \(\mathrm{NO}\) (c) \(\mathrm{NO}_{2}\) (d) \(\mathrm{N}_{2} \mathrm{O}_{3}\)

Step-by-Step Solution

Answer

The nitric acid anhydride is (a) \( \mathrm{N}_2 \mathrm{O}_5 \).

Step 1: Understanding Anhydrides

An anhydride is a compound derived from another compound, usually an acid, by removing water. Specifically, an acid anhydride is formed from the dehydration of an acid. Nitric acid ( HNO_3) can lose a water molecule to form an anhydride.

Step 2: Form the Molecular Formula for Nitric Acid Anhydride

Start with the chemical formula of nitric acid, HNO_3. Remove one unit of H_2O (a water molecule) from this formula to find the formula of its anhydride. The result is N_2O_5.

Step 3: Compare with Given Options

Examine the given options: (a) N_2O_5, (b) NO, (c) NO_2, and (d) N_2O_3. We know from Step 2 that nitric acid anhydride is N_2O_5, which matches option (a).

Key Concepts

Chemical Anhydrides

Chemical anhydrides are fascinating compounds. They derive from acids by losing a water molecule. Often, you find that they react with water to regenerate the original acid. This makes them quite reactive and versatile in chemistry.

In organic chemistry, anhydrides are indispensable. They act as reagents in many synthesis reactions. For example, acetic anhydride is commonly used to introduce acetyl groups. By removing water from an acid, chemists can obtain an anhydride. This loss usually involves two acidic molecules losing one water molecule between them. Acid anhydrides include not just simple molecules but large polymers too.

When it comes to inorganic chemistry, as in the case of nitric acid anhydride, the process is similar. By stripping away water from nitric acid, we get a simpler compound, essential in different chemical processes. Anhydrides hold a special place in the realm of chemistry for their unique properties.

Nitric Acid

Nitric acid, \\( HNO_3 \), is a potent and highly corrosive mineral acid. It's widely used owing to its dynamic chemical properties. You often find it in industries involving fertilizers, explosives, and even in food processing.

Nitric acid can participate in various reactions due to its ability to donate protons. It's known mainly for forming nitrates from reactions with metals. Besides its industrial applications, it's also essential in laboratory settings for cleaning glassware or as a reagent.

Given its reactivity, nitric acid is often neutralized to form less harmful substances when used in specific processes. Encountering nitric acid requires careful handling. Its rich chemistry and ability to form diverse molecules make it indispensable in numerous fields.

Dehydration Reaction

Dehydration reactions are critical in both organic and inorganic chemistry. These reactions occur when a molecule loses water. This conversion often changes the structure and properties of the original substance.

In organic chemistry, dehydration forms alkenes or joins together small molecules into larger polymers. Alcohols, for instance, lose a water molecule to form alkenes under acidic conditions. In biochemical systems, dehydration synthesis links monomers into polymers, essential for forming complex carbohydrates and proteins.

In inorganic scenarios, such as forming nitric acid anhydride, a simple dehydration reaction removes water from nitric acid. This change results in a more reactive molecule, like \\( N_2O_5 \). Dehydration thus rearranges molecular structures to create new possibilities in synthesis and material science.

Overall, dehydration reactions are pivotal in developing both everyday materials and specialized chemicals. Understanding them allows for broader applications and novel discoveries in scientific fields.