Question

Bleaching powder contains a salt of an oxoacid as one of its components. The anhydride of that oxoacid is (A) \(\mathrm{Cl}_{2} \mathrm{O}\) (B) \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) (C) \(\mathrm{ClO}_{2}\) (D) \(\mathrm{Cl}_{2} \mathrm{O}_{6}\)

Short answer

The anhydride of the oxoacid in bleaching powder is \(\mathrm{Cl_2O}\) which corresponds to option (A).

Step-by-step solution

Identify the Salt in Bleaching Powder

Bleaching powder is commonly calcium hypochlorite, which has the chemical formula \(\mathrm{Ca(OCl)_2}\). The hypochlorite ion \(\mathrm{OCl}^-\) comes from the hypochlorous acid \(\mathrm{HClO}\).

Determine the Oxoacid

The oxoacid from which \(\mathrm{Ca(OCl)_2}\) is derived is hypochlorous acid \(\mathrm{HClO}\).

Find the Anhydride of the Oxoacid

The anhydride of an acid is typically an oxide that, when combined with water, will form the acid. For hypochlorous acid \(\mathrm{HClO}\), the anhydride would be the oxide of chlorine where each chlorine atom is bonded to one oxygen, resulting in the formula \(\mathrm{Cl_2O}\).

Key concepts

Calcium Hypochlorite

Calcium hypochlorite is a widely used chemical compound with the formula \( \mathrm{Ca(OCl)_2} \). It's an essential ingredient in bleaching powder and is known for its disinfecting and bleaching properties. This versatile substance is deployed in various applications, from sanitizing drinking water to maintaining the cleanliness of swimming pools.

Its connection to bleaching powder lies in the chemistry of the hypochlorite ion (\( \mathrm{OCl}^- \)), which is responsible for the compound's bleaching action. When introduced to water, calcium hypochlorite releases hypochlorous acid and calcium hydroxide, initiating a strong oxidation process that removes colors and stains and kills pathogens. Due to its potency and ease of use, it has become a mainstay in household and industrial cleaning products.

Oxoacids

Oxoacids, a group of acids characterized by oxygen bound to hydrogen and another element, play a crucial role in various chemical processes. The 'oxo' component signifies the presence of oxygen in the molecular structure. Generally speaking, oxoacids contain at least one hydrogen atom, which is capable of dissociating to form a proton, and an electronegative element (such as sulfur, nitrogen, or, as in our focus, chlorine), which is bonded to oxygen.

In aqueous solutions, oxoacids can release hydrogen ions contributing to the solution's acidity. These compounds are fundamental in preparing salts and disinfectants and are also pivotal in environmental chemistry processes such as the formation of acid rain. For students diving into this topic, understanding oxoacids is essential for grasping the behavior and reactions of many household and industrial chemicals.

Chemical Anhydrides

Chemical anhydrides are compounds that can be considered as derived from other compounds (usually acids) by the removal of water molecules. When it comes to acids, the term 'anhydride' implies a dehydration reaction where two acid molecules combine to form one molecule of anhydride and one molecule of water. This process is particularly important in organic chemistry and in the formation of various inorganic oxides.

Anhydrides are valuable in synthesis and industrial applications because they often react more readily than their acid precursors, making them efficient agents for transferring acyl groups or forming oxides. When studying the anhydrides of oxoacids, one should note that they can be reverted to the original acids simply by adding water, a process that is central to many chemical production and purification processes.

Hypochlorous Acid

Hypochlorous acid (\( \mathrm{HClO} \)) is a weak, yet significant oxoacid, particularly noted for its efficacy as a disinfectant. While it may not be as strong as some other acids, it compensates with its potent oxidative properties that make it an excellent choice for sanitation and disinfection.

In aqueous solution, hypochlorous acid partly dissociates into the hypochlorite ion (\( \mathrm{OCl}^- \)) and a hydrogen ion (\( \mathrm{H}^+ \)), contributing to its acidic nature. It is formed when chlorine dissolves in water and finds uses in various sectors including water treatment, wound care, and the food industry. For students learning about hypochlorous acid, it's important to understand its role in the formulation of cleaning agents and its dynamic equilibrium in solution, which is pH-dependent.