Problem 145 - Introductory Chemistry Atoms First

Question

Give the molecular formula for hypochlorous acid and perchloric acid.

Step-by-Step Solution

Answer

The molecular formulas for the given acids are: - Hypochlorous acid: \(HClO\) - Perchloric acid: \(HClO_4\)

Step 1: Identifying Hypochlorous Acid

Hypochlorous acid is an oxyacid of chlorine with the formula HClO. In this molecule, chlorine (Cl) is bonded to one hydroxyl (-OH) group, making it an acid. The molecular formula for hypochlorous acid is \(HClO\).

Step 2: Identifying Perchloric Acid

Perchloric acid is a stronger oxyacid of chlorine with the molecular formula HClO4. In this molecule, chlorine (Cl) is bonded to four oxygen atoms arranged as three double-bonded oxygens and one hydroxyl group (-OH). The molecular formula for perchloric acid is \(HClO_4\). In summary, the molecular formulas for the given acids are: - Hypochlorous acid: \(HClO\) - Perchloric acid: \(HClO_4\)

Key Concepts

Hypochlorous Acid

Hypochlorous acid, with its molecular formula of \(HClO\), represents a class of compounds known as oxyacids. Oxyacids are acids that contain oxygen, hydrogen, and another element, which in this case is chlorine. In hypochlorous acid, the chlorine atom is covalently bonded to an oxygen atom and a hydrogen atom is attached to the oxygen, forming the hydroxyl group. This weak acid is commonly used in disinfectants and bleaching applications, and it’s also naturally produced by the body's immune cells to fight infection.

Hypochlorous acid is considered a weak acid due to its tendency to partially dissociate in aqueous solution, releasing hydrogen ions (\(H^+\)) and hypochlorite ions (\(OCl^-\)), which are responsible for its oxidizing properties. It is important to note that despite its weak acidic strength, hypochlorous acid is highly effective as a disinfectant, precisely because of its ability to oxidize and thereby destroy various pathogens.

Perchloric Acid

Perchloric acid stands out with its molecular formula \(HClO_4\) as an even more compelling oxyacid of chlorine. Unlike hypochlorous acid, perchloric acid is a strong acid and fully dissociates in water. The structure of perchloric acid includes a central chlorine atom surrounded by a tetrahedral arrangement of oxygen atoms. One of these is a hydroxyl group, while the other three oxygen atoms are double-bonded to chlorine.

This strong acid has significant industrial applications due to its potent oxidative abilities, which can be hazardous if not handled properly. Perchloric acid is a powerful oxidizing agent and, as such, is employed in chemical synthesis and analysis. Its uses range from rocket fuel oxidizer to laboratory reagent for analytical chemistry, illustrating the diverse applications enabled by its reactivity and strength. When studying perchloric acid, one must exercise caution due to its highly reactive and corrosive nature, especially when in high concentrations.

Oxyacid of Chlorine

Oxyacids of chlorine are acids that consist of chlorine, oxygen, and hydrogen atoms. The basic formula for these acids is \(HClO_n\), where \(n\) indicates the number of oxygen atoms bonded to chlorine. The strength of the oxyacid depends on the number of oxygen atoms; generally, as the number of oxygen atoms increases, so does the acidity and oxidizing strength of the acid.

Examples of chlorine oxyacids include not only hypochlorous acid (\(HClO\)) and perchloric acid (\(HClO_4\)), but also chlorous acid (\(HClO_2\)) and chloric acid (\(HClO_3\)). These acids are widely used in various industries, from water treatment to the synthesis of organic and inorganic compounds. It is fascinating how the varying number of oxygen atoms can greatly influence the properties and uses of these acids. For instance, while hypochlorous acid is an effective disinfectant at lower concentrations, perchloric acid's high oxidizing capacity is harnessed in more demanding applications such as rocket fuel.