Problem 82 - Chemistry The Central Science In Si Units

Question

What is the anhydride for each of the following acids: (c) \(\mathrm{HNO}_{2}\) (a) \(\mathrm{H}_{2} \mathrm{SO}_{4},\) (b) \(\mathrm{HClO}_{3}\), (d) \(\mathrm{H}_{2} \mathrm{CO}_{3}\), (e) \(\mathrm{H}_{3} \mathrm{PO}_{4} ?\)

Step-by-Step Solution

Answer

The anhydrides are (a) SO₃, (b) Cl₂O₅, (c) N₂O₃, (d) CO₂, (e) P₂O₅.

Step 1: Introduction to Acid Anhydrides

An acid anhydride is typically formed by the removal of water (H₂O) from an acid. For most inorganic oxyacids, the corresponding anhydride is formed by removing one or more moles of water from the acid molecule.

Step 1: Identify Acid Anhydride for H₂SO₄

For \(\mathrm{H}_2\mathrm{SO}_4\), the corresponding anhydride is \('\mathrm{SO}_3\). This is because removing one molecule of water from \(\mathrm{H}_2\mathrm{SO}_4\) results in sulfur trioxide \(\mathrm{SO}_3\).

Step 2: Identify Acid Anhydride for HClO₃

For \(\mathrm{HClO}_3\), the corresponding anhydride is \(\mathrm{Cl}_2\mathrm{O}_5\). Chlorine heptoxide \(\mathrm{Cl}_2\mathrm{O}_5\) is obtained by removing water from two molecules of chloric acid.

Step 3: Identify Acid Anhydride for HNO₂

For \(\mathrm{HNO}_2\), the related anhydride is \(\mathrm{N}_2\mathrm{O}_3\). Nitrogen trioxide is formed by the removal of water from two molecules of nitrous acid.

Step 4: Identify Acid Anhydride for H₂CO₃

For \(\mathrm{H}_2\mathrm{CO}_3\), the anhydride is \(\mathrm{CO}_2\). Carbon dioxide is formed by losing a molecule of water from carbonic acid.

Step 5: Identify Acid Anhydride for H₃PO₄

For \(\mathrm{H}_3\mathrm{PO}_4\), the corresponding anhydride is \(\mathrm{P}_2\mathrm{O}_5\) (diphosphorus pentoxide). This compound forms by losing water from phosphoric acid.

Key Concepts

Understanding Inorganic Oxyacids

Inorganic oxyacids are a fascinating class of acids defined by the presence of oxygen within their structural composition. These acids are primarily composed of hydrogen (H), oxygen (O), and a central nonmetallic element. Common examples of inorganic oxyacids include sulfuric acid (\(\text{H}_2\text{SO}_4\)), nitric acid (\(\text{HNO}_3\)), and phosphoric acid (\(\text{H}_3\text{PO}_4\)). The presence of oxygen is what differentiates these from other categories of acids.
Inorganic oxyacids play significant roles in various sectors due to their diverse chemical properties.
They are crucial in industrial applications, fertilizer production, and laboratory reagents.

• They generally have different strengths and correspond to unique behaviors when dissolved in water.
• The number of oxygen atoms bonded to the central atom often influences their acidity and chemical reactivity.

The Role of Water in Anhydride Formation

Water removal is central to the conversion process from acids to their anhydrides. An acid anhydride is an oxide that forms when an inorganic oxyacid loses one or more molecules of water (H₂O).
For instance, sulfuric acid (\(\text{H}_2\text{SO}_4\)) loses a molecule of water to form sulfur trioxide (\(\text{SO}_3\)).
This transformation is what we call an "anhydride formation," signifying the absence of water. Here are some key points about the exclusion of water in anhydrides:

• The dehydration process of these acids generally leads to the formation of gaseous or solid anhydrides.
• Not all acid molecules release the same number of water molecules. The stoichiometry of the acid determines how many molecules of water are removed.

Steps of Anhydride Formation

Anhydride formation involves a chemical transformation where an oxyacid loses water (H₂O). The resulting substance is often more reactive.
Consider these steps:

• Identify the Acid: Begin by recognizing the formula of the oxyacid, like (\(\text{H}_3\text{PO}_4\)).
  
• Determine Water Loss: Decide how the formula changes when water is removed. Compare the original acid to determine the "lost" elements.
  
• Create the Anhydride: After water removal, the remaining atoms form the anhydride. For phosphoric acid, this results in diphosphorus pentoxide (\(\text{P}_2\text{O}_5\)).

This method of sequential dehydration helps clarify how inorganic acids translate into anhydrides, leading to practical examples in understanding basic chemistry.

Essentiality of Acid Chemistry

Acid chemistry is foundational in understanding both biological processes and industrial applications.
Acids participate in reactions that, for instance, vary from stomach digestion to the creation of battery acids.
The properties of oxyacids make them distinctive in their ability to transfer protons and produce acidic solutions when mixed with water.

• Acidity in many oxyacids is determined by the concentration and bonding pattern of the hydrogen.
  
• In industry, sulfuric acid is a notable player due to its role as an effective dehydrating agent as well as a strong acid.

Understanding the chemical makeup of acids and their formation of anhydrides is crucial for harnessing their potential in both synthesis and nature.