Problem 87 - Chemistry: The Central Science

Question

What is the anhydride for each of the following acids: (a) \(\mathrm{H}_{2} \mathrm{SO}_{4},(\mathrm{~b}) \mathrm{HClO}_{3},(\mathrm{c}) \mathrm{H} \mathrm{NO}_{2},(\mathrm{~d}) \mathrm{H}_{2} \mathrm{CO}_{3},(\mathrm{e}) \mathrm{H}_{3} \mathrm{PO}_{4} ?\)

Step-by-Step Solution

Answer

The anhydrides of the given acids are: (a) \(\mathrm{SO}_{3}\), (b) \(\mathrm{Cl}_{2} \mathrm{O}_{5}\), (c) \(\mathrm{N}_{2} \mathrm{O}_{3}\), (d) \(\mathrm{CO}_{2}\), and (e) \(\mathrm{P}_{2} \mathrm{O}_{5}\).

Step 1: (a) Anhydride of \(\mathrm{H}_{2} \mathrm{SO}_{4}\)

To find the anhydride of \(\mathrm{H}_{2} \mathrm{SO}_{4}\), remove one water molecule (H\(_{2}\)O) from the formula and adjust: \[ \mathrm{H}_{2} \mathrm{SO}_{4} - \mathrm{H}_{2} \mathrm{O} = \mathrm{SO}_{3} \] The anhydride of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is \(\mathrm{SO}_{3}\).

Step 2: (b) Anhydride of \(\mathrm{HClO}_{3}\)

To find the anhydride of \(\mathrm{HClO}_{3}\), remove one water molecule (H\(_{2}\)O): \[ 2\mathrm{HClO}_{3} - \mathrm{H}_{2} \mathrm{O} = \mathrm{Cl}_{2} \mathrm{O}_{5} \] The anhydride of \(\mathrm{HClO}_{3}\) is \(\mathrm{Cl}_{2} \mathrm{O}_{5}\).

Step 3: (c) Anhydride of \(\mathrm{HNO}_{2}\)

To find the anhydride of \(\mathrm{HNO}_{2}\), remove one water molecule (H\(_{2}\)O) and\nadjust the formula: \[ 2\mathrm{HNO}_{2} - \mathrm{H}_{2} \mathrm{O} = \mathrm{N}_{2} \mathrm{O}_{3} \] The anhydride of \(\mathrm{HNO}_{2}\) is \(\mathrm{N}_{2} \mathrm{O}_{3}\).

Step 4: (d) Anhydride of \(\mathrm{H}_{2} \mathrm{CO}_{3}\)

To find the anhydride of \(\mathrm{H}_{2} \mathrm{CO}_{3}\), remove one water molecule (H\(_{2}\)O) and adjust the formula: \[ \mathrm{H}_{2} \mathrm{CO}_{3} - \mathrm{H}_{2} \mathrm{O} = \mathrm{CO}_{2} \] The anhydride of \(\mathrm{H}_{2} \mathrm{CO}_{3}\) is \(\mathrm{CO}_{2}\).

Step 5: (e) Anhydride of \(\mathrm{H}_{3} \mathrm{PO}_{4}\)

To find the anhydride of \(\mathrm{H}_{3} \mathrm{PO}_{4}\), remove one water molecule (H\(_{2}\)O) and adjust the formula: \[ 2\mathrm{H}_{3} \mathrm{PO}_{4} - \mathrm{H}_{2} \mathrm{O} = \mathrm{P}_{2} \mathrm{O}_{5} \] The anhydride of \(\mathrm{H}_{3} \mathrm{PO}_{4}\) is \(\mathrm{P}_{2} \mathrm{O}_{5}.\)

Key Concepts

Sulfuric Acid

Sulfuric acid, with the chemical formula \( \mathrm{H}_{2} \mathrm{SO}_{4} \), is a highly potent acid. It is widely used in various industries for manufacturing processes, including fertilizers and chemicals. To understand its anhydride, we remove a molecule of water from its formula. This process results in sulfur trioxide, \( \mathrm{SO}_{3} \).
Removing water molecules from acids to form acid anhydrides is important in understanding acid properties and behavior.

• Sulfuric acid is a strong acid commonly found in car batteries.
• Creating \( \mathrm{SO}_{3} \) from \( \mathrm{H}_{2} \mathrm{SO}_{4} \) showcases a typical reaction in chemical synthesis.

Be careful when handling sulfuric acid, as it is high in corrosivity and can cause serious harm on contact.

Carbonic Acid

Carbonic acid, \( \mathrm{H}_{2} \mathrm{CO}_{3} \), is an important compound in the carbon cycle, naturally occurring in rainwater and carbonated beverages. It is a weak acid and is in equilibrium with carbon dioxide and water.
When determining its anhydride, we remove a water molecule, resulting in carbon dioxide \( \mathrm{CO}_{2} \). This transformation highlights how carbonic acid plays a crucial role in biological and environmental systems.

• Key in regulating pH levels in living organisms.
• Used in the production of soft drinks and sparkling water.

This interplay of carbon dioxide with water demonstrates significant environmental implications such as ocean acidification.

Phosphoric Acid

Phosphoric acid is known for its formula, \( \mathrm{H}_{3} \mathrm{PO}_{4} \). Commonly used in industry, food, and dentistry, it's a less corrosive acid compared to sulfuric acid. Designing its anhydride involves removing water to derive phosphorus pentoxide, \( \mathrm{P}_{2} \mathrm{O}_{5} \).

• Catalyst in dehydration reactions, particularly in organic chemistry.
• Contributes to controlling acidity in foods and beverages.

Understanding this removal process helps in appreciating phosphoric acid's utility in processing minerals and substances efficiently.

Nitrous Acid

Nitrous acid, \( \mathrm{HNO}_{2} \), is a weak and unstable acid usually present in aqueous solution. It is often utilized in diazotization reactions crucial for synthesizing azo dyes.
Its anhydride is formed by removing water, resulting in dinitrogen trioxide, \( \mathrm{N}_{2} \mathrm{O}_{3} \). Such transformations are foundational for grasping inorganic reaction dynamics:

• Used to produce alkali-free nitrite solutions.
• Breaks down readily, beneficial for certain organic syntheses.

Due to its instability, nitrous acid needs appropriate handling measures to ensure safety.

Perchloric Acid

Perchloric acid, \( \mathrm{HClO}_{4} \), known for being a superacid, is applied in rocket propellant systems and analytical chemistry.
When its anhydride, \( \mathrm{Cl}_{2} \mathrm{O}_{7} \), is formed through water removal, you see the nucleus’s extreme oxidative potential.

• Utilized in etching and as a catalyst in organic reactions.
• Favored for its strong oxidizing capabilities when used under controlled conditions.

Understanding perchloric acid and its transformations are essential for safely producing energetic materials.