Problem 134 - General Chemistry: Principles and Modern Applications

Question

What is the acid anhydride of \((a) \mathrm{H}_{2} \mathrm{SO}_{4} ;(\mathrm{b}) \mathrm{H}_{2} \mathrm{SO}_{3}\) (c) \(\mathrm{HClO}_{4} ;\) (d) \(\mathrm{HIO}_{3}\) ?

Step-by-Step Solution

Answer

The acid anhydrides are: (a) \(H_{2}S_{2}O_{7}\), (b) \(H_{2}S_{2}O_{5}\), (c) none, (d) none.

Step 1 Find the Acid Anhydride of \(H_{2}SO_{4}\)

Start by taking two moles of \(H_{2}SO_{4}\) and remove one water (\(H_{2}O\)). Let's write the reaction as \(2 H_{2}SO_{4} -> Anhydride + H_2O\). The anhydride for \(H_{2}SO_{4}\) will be \(H_{2}S_{2}O_{7}\).

Step 2 Find the Acid Anhydride of \(H_{2}SO_{3}\)

In a similar way for \(H_{2}SO_{3}\), remove one water from two moles of the acid. So the equation looks like this: \(2 H_{2}SO_{3} -> Anhydride + H_2O\). The anhydride for \(H_{2}SO_{3}\) will be \(H_{2}S_{2}O_{5}\).

Step 3 Find the Acid Anhydride of \(HClO_{4}\)

For \( HClO_{4}\), as it's based on a single atom central element (Chlorine), it typically won't form an anhydride. The removal of water from two moles of this substance is not possible. So, no anhydride for \(HClO_{4}\).

Step 4 Find the Acid Anhydride of \(HIO_{3}\)

Meanwhile for \(HIO_{3}\), it's similar to \(HClO_{4}\). Being based on single atom central element (Iodine), it cannot form an anhydride by losing water from two moles. Therefore, no anhydride for \(HIO_{3}\).

Key Concepts

Sulfuric Acid

Sulfuric acid, represented by the chemical formula \(H_2SO_4\), is a strong mineral acid known for its wide range of applications. It is a colorless, oily liquid that is soluble in water with a strong acidic nature. In industrial contexts, sulfuric acid is crucial for the production of fertilizers, in petroleum refining, and in chemical synthesis. To find the acid anhydride of sulfuric acid, we consider what happens when we remove a molecule of water \(H_2O\) from two molecules of sulfuric acid.

This reaction results in the compound \(H_2S_2O_7\), known as pyrosulfuric acid or oleum. Oleum allows for the concentration of sulfuric acid to high levels in industries and plays a critical role in the contact process of sulfuric acid production.

• Sulfuric acid is a key agent in dehydrating reactions.
• It is also utilized in the manufacture of hydrofluoric acid and phosphoric acid.
• The compound \(H_2S_2O_7\) is highly versatile in industrial chemical reactions.

Sulfurous Acid

Sulfurous acid is another important sulfur-based acid, with the chemical formula \(H_2SO_3\). Unlike sulfuric acid, sulfurous acid is less stable and exists primarily in solution form. It plays a role in applications such as preserving food and in bleaching. This acid is formed when sulfur dioxide \(SO_2\) dissolves in water.

To identify its acid anhydride, sulfurous acid follows a similar approach as sulfuric acid with the removal of water from its molecules. Removing a molecule of water from two moles of \(H_2SO_3\) leads to the formation of \(H_2S_2O_5\), the anhydride of sulfurous acid.

• It is less stable than its sulfuric counterpart.
• It can decompose and revert back to sulfur dioxide on heating.
• Known for its use in food preservation due to its antibacterial properties.

Perchloric Acid

Perchloric acid, \(HClO_4\), represents one of the strongest acids known. In its pure form, it is a colorless liquid and an extremely powerful oxidizer. Unlike sulfuric and sulfurous acids, perchloric acid does not form an anhydride because the central chlorine atom does not allow the loss of water through an anhydride formation process.

Perchloric acid is especially important in analytical chemistry, serving as a reagent in determining the presence of other substances.

• Used in making explosives and rocket fuel.
• Has an oxidizing strength greater than sulfuric acid.
• Demands careful handling due to its highly reactive nature.

Iodic Acid

Iodic acid is another strong acid, noted by its formula \(HIO_3\). This acid occurs as a colorless solid with exceptional oxidizing capabilities. Like perchloric acid, iodic acid is unable to form an anhydride because the central iodine atom does not facilitate the formation of an anhydride by simple water molecule removal.

In practical applications, iodic acid is predominantly used in the analysis of substances that require oxidation, and it plays a role in organically synthesizing iodine compounds.

• Often used in chemical analysis as an oxidant.
• Finds use in the preparation of iodates.
• An essential substance in organic chemistry for iodine synthesis.