Stronger acid than nitric acid, sulfuric acid, and hydrochloric acid; It is Perchloric acid (HClO4) also called Hyperchloric acid or hydroxidotrioxidochlorine

With the chemical formula HClO₄, Perchloric acid is a chlorine oxoacid. It is a mineral acid also known as hydroxidotrioxidochlorine and hyperchloric acid. This colourless chemical, which is often found as an aqueous solution, is a stronger acid than sulfuric acid, nitric acid, and hydrochloric acid. When hot, it is a potent oxidant, although at room temperature, aqueous solutions up to about 70% by weight are often harmless, exhibiting only strong acid characteristics and no oxidising properties. Perchloric acid is one of the strongest Bronsted-Lowry acids as it functions as a super acid.

At room temperature, anhydrous perchloric acid is an oozy, unstable liquid. It produces at least five hydrates, several of which have undergone crystallographic characterization. These solids are made up of the perchlorate anion connected to H₂O and H₃O⁺ centers by hydrogen bonds. Perchlorate of hydronium is one instance. With water, perchloric acid forms an azeotrope that contains roughly 72.5% perchloric acid. This acid is readily available in the marketplace and is permanently stable. These substances are hygroscopic. As a result, concentrated perchloric acid dilutes itself when exposed to the air by absorbing water from the atmosphere. It corrodes both metals and tissue. Perchloric acid in closed containers that have been exposed to heat for a long time may violently burst.

The compound poses a fire and explosion risk since it is a strong oxidant and interacts violently with combustible and reducing substances, organic substances, and strong bases. It affects numerous metals, producing explosive/flammable gas. If the concentration is greater than 72%, the acid is unstable and may explode by shock or concussion when dry or drying. At normal temperature, mixtures containing flammable material, like paper, may spontaneously ignite. Never pour water directly into perchloric acid; instead, add the acid slowly to the water to dissolve or dilute.

Given that both substances are potent oxidizers, its risks resemble those of nitric acid in many ways. A further danger from perchloric acid is that its mist and vapour it can condense and form explosive metallic perchlorates in ventilation systems.

If a substance produces protons in an aqueous solution, it is referred to as an acid, and if its conjugate base is stable, it is referred to as a strong acid. Because of the negative charge conjugation that has formed on the oxygen atom and on all three other oxygen atoms in this instance, the perchlorate ion is stable.

A strong acid is one that readily releases hydrogen, hence the term. The readiness of the hydrogen atom to separate from the molecule depends on the central atom's oxidation number when it is in a different oxidation state than in the instances given above. The most common form of sulfuric acid is H₂SO₄ and sulphur has an oxidation number of +6. HClO₄ has a chlorine oxidation number of +7 while HClO₃ has a chlorine oxidation number of +5. As a result, perchloric acid's HClO₄ bond is the weakest, making it our choice for the strongest acid. Additionally, it is more potent than the most common nitric acid. Perchloric acid has a Cl oxidation state of +7 while sulphuric acid has a S oxidation state of +6. The O-H bond breaks more rapidly the more oxidised the core atom, making the acid stronger.

In contrast to other noncoordinating anion acids like hexafluorophosphoric acid and fluoroboric acid, which exhibit substantial susceptibility to hydrolysis, perchloric acid is weakly nucleophilic in nature and has little susceptibility to hydrolysis.

Caution:

Keep in mind that although being highly caustic by nature, perchloric acid is useful in rocketry due to the mixes it may create. We can also remark that since there are three oxygen atoms, they will pull oxygen hydrogen's electrons toward them, weakening the bond.

Process:

There are two methods for producing perchloric acid industrially. The high aqueous solubility of sodium perchlorate (209 g/100 mL of water at room temperature) is taken advantage of by the conventional approach. When such solutions are treated with hydrochloric acid, perchloric acid results, which precipitates solid sodium chloride

 NaClO₄ + HCl → NaCl + HClO₄

By distilling, the concentrated acid can be made pure. Anodic oxidation of aqueous chlorine at a platinum electrode is the more direct and salt-free alternative approach.

Acetic anhydride, which interacts with the water in perchloric acid to produce an anhydrous combination, is used to remove water from perchloric acid.

 

Uses:

• Ammonium perchlorate, a crucial component of rocket fuel, can be prepared with the help of perchloric acid, which is also useful for other perchlorate salts. Perchloric acid is very corrosive and easily creates mixes that could explode. As a result, perchloric acid is regarded as a crucial chemical in the space industry.
• In the process of separating sodium and potassium, perchloric acid is utilised as an oxidizer.
• Additionally, this substance is employed in the etching of liquid crystal display devices (often abbreviated to LCD). As a result, perchloric acid is also frequently utilised in the electronics sector.
• To separate potassium from sodium, as well as in other scientific experiments and commercial procedures, perchloric acid is utilised. As a result of its special characteristics, this substance is used in analytical chemistry.
• Used as a catalyst for the electropolishing or etching of molybdenum and chrome, as a reagent to determine the 1H-Benzotriazole, for plating metals, and in the manufacture of explosives.
• It is employed in the production of optical equipment, chemical products, fertiliser, and rust removal.
• In addition, perchloric acid is used in the extraction of materials from their ores in a number of significant ways.
• The perchloric acid salts are used in explosives and metal plating, among other things. Perchloric acid has the potential to detonate and releases toxic and corrosive vapours when heated.

Researchers should bear the following in mind while using or anticipating utilising perchloric acid in their experiments:

• Currently, there are no fume hoods on campus that can accommodate perchloric acid digestions in a secure manner. Due to the significant cost of cleaning these wash-down hoods of perchlorate pollution, any surviving hoods have been decommissioned and won't be turned back on.
• At no point should solvents be kept close to a designated perchloric acid location. These locations need to be marked with a sign that reads "Use Only Perchloric Acid. Organic Chemicals Are Not Allowed."
• Always add acid to water, not the other way around, using diluted perchloric acid (or any other acid).
• Researchers' tissues are just as susceptible to perchloric acid damage as sample tissue is. When handling perchloric acid, safety equipment such as goggles or face shields, gloves, and an apron are required.
• Until a perchloric acid digesting hood has been completely decontaminated, no work should be done in it due to the risk of an explosion.
• No garbage containing perchloric acid should be combined with any other waste. It should be placed in acid-resistant bottles (ideally the acid's original container), identified as hazardous chemical waste, and handled accordingly.
• Perchloric acid needs to be stored inside secondary containment, apart from all other compounds (such as a pyrex baking dish or plastic dish pan). It must not be kept next to bases, other organic or combustible materials, or organic acids like acetic acid.