Perchloric Acid Formula – Structure, Properties, Uses, Sample Questions

Perchloric Acid consists of the elements Hydrogen, Chlorine, and Oxygen. Hydrogen is the lightest known element that exists. It is a colorless, odorless, tasteless, and flammable gas. Its atomic number is 1 and is represented by the symbol H. Chlorine is a toxic and corrosive gas present in group 17 of the periodic table. It is the second lightest element in the halogen group. Its atomic number is 17 and is represented by the symbol Cl. Oxygen is a highly reactive nonmetal present in group-16 of the periodic table. Its atomic number is 8 and is represented by the symbol O.

Perchloric Acid is an oxoacid of chlorine with the chemical formula HClO₄. It is a mineral acid which generally found in an aqueous solution. Perchloric acid is colorless, odorless aqueous solution. This acid is stronger than nitric acid and sulfuric acid. Perchloric acid is corrosive to tissue and metals. The other names for Perchloric acid are Hydroxidotrioxidochlorine, Hyperchloric acid. It is mainly used to prepare ammonium perchlorate which is an important rocket fuel component.

Preparation of Perchloric Acid

• Perchloric Acid is prepared by treating the solution of Sodium perchlorate with hydrochloric acid. The chemical reaction is mentioned below-

NaClO₄ + HCl ⇢ NaCl + HClO₄

• In laboratories, Perchloric Acid is prepared by treating Barium perchlorate with Sulphuric acid which precipitates Barium sulfate and leaves Perchloric acid.

Ba(ClO₄)₂ +  H₂SO₄ ⇢ BaSO₄ + 2HClO₄

• Perchloric Acid is prepared from Chloric Acid (HClO₃) by evaporating the chloric acid. The reaction of it is given below-

3HClO₃ → HClO₄ + Cl₂ + 2O₂ + H₂O

• The other way to it prepare Perchloric Acid is by mixing Nitric acid (HNO₃) with Ammonium perchlorate (NH₄ClO₄) and adding hydrochloric acid (HCl) while it is boiling.

Structure of Perchloric Acid

Perchloric Acid consists of one Chlorine atom, four Oxygen atoms, and one Hydrogen atom. Its molecular formula is HClO₄. In the Perchloric Acid, H+ is attached to an oxygen atom, which forms a single bond with Chlorine. The remaining 3 oxygen atoms are bonded with chlorine with a coordinate bond. 

Perchloric Acid Structure

Physical Properties of Perchloric Acid

• The appearance of Perchloric Acid is a colorless aqueous solution.
• Molecular weight of Perchloric Acid is 100.46 g/mol
• Its melting point is -17 °C.
• Boiling point of Perchloric acid is 203 °C.
• Density of Perchloric acid is 1.768 g/cm³.

Chemical Properties of Perchloric Acid

• When a suspension of iodine is heated with Perchloric acid to generate Para periodic acid. The chemical reaction is given below-

2HClO₄ + l₂ + 4H₂O → 2H₅IO₆ + Cl₂

• Perchloric acid is a strong acid and the conjugated base of the Perchloric acid is stable and almost completely dissociated in an aqueous solution.

HClO₄ + H₂O → H₃O⁺ + ClO₄^–

• Distillation of Perchloric acid in presence of dehydrating agent- Phosphorous pentoxide to produce dichlorine heptoxide.

2HClO₄ + P₄O₁₀ → Cl₂O₇ + H₂P₄O₁₁

Uses of Perchloric Acid

• Perchloric Acid is used to separate potassium from sodium.
• It is used to prepare ammonium perchlorate which is an important rocket fuel component.
• Perchloric Acid is used in making explosives.
• It is used in metal refinement, fertilizer, and rust removal.
• Perchloric Acid is used for plating metals.
• Used in the production of optical equipment and chemical products.

Why Perchloric Acid is considered a Strong acid?

A compound is referred to be acid if it furnishes proton in the aqueous solution and is said to be a strong acid if its conjugate base is stable. In this case, the perchlorate ion’s stability is because of the negative charge conjugation developed on the oxygen atom, overall the 3 other oxygen atoms.

Perchloric acid is weakly nucleophilic in nature and has negligible susceptibility to hydrolysis compared to other noncoordinating anion acids like hexafluoro phosphoric acid, and fluoroboric acid which show high susceptibility to hydrolysis.

Health Hazards

• Inhalation of the Perchloric Acid vapor causes coughing, irritation in the lungs, and a burning sensation in the nose and throat.
• Ingestion of this compound cause stomach burns.
• Prolonged exposure to the vapor of Perchloric Acid leads to vomiting.
• On heating, it liberates toxic gases.

Sample Questions

Question 1: Is Perchloric Acid dangerous?

Answer:

Perchloric Acid is a reactive compound. It is highly reactive towards many metals and organic matter. It is corrosive to skin. Prolonged exposure causes vomiting. Ingestion of Perchloric Acid cause burns in the stomach. So while handling Perchloric Acid, adequate safety measures has to be followed. 

Question 2: How Perchloric Acid is prepared from HClO₃?

Answer:

Perchloric Acid is prepared from chloric acid (HClO₃) by evaporating the chloric acid. The reaction of it is given below

3HClO₃ → HClO₄ + Cl₂ + 2O₂ + H₂O

Question 3: Find the molecular weight of Perchloric Acid?

Answer:

The molecular formula of Perchloric Acid is HClO₄.

Atomic weight of hydrogen = 1.00784 

Atomic weight of Chlorine = 35.453

Atomic weight of Oxygen = 15.999

Molar mass = 1.00784 + 35.453 + (4 × 15.999)

=100.46

Question 4: Is Perchloric Acid is Hygroscopic compound?

Answer:

Perchloric Acid is Hygroscopic in nature because it forms azeotrope with water which consists 72.5% of perchloric acid (HClO₄).

Question 5: How to make Perchloric Acid an anhydrous compound?

Answer:

In order to remove water from Perchloric Acid,  Acetic anhydride is used which reacts with water present in the perchloric acid making the resulting mixture anhydrous.

Question 6: What are the uses of Perchloric Acid?

Answer:

Perchloric Acid is used in making explosives, preparation of ammonium perchlorate which is an important component in rocket fuel, metal plating, preparation of optical equipment. It is also used in fertilizers, removing rust and metal refinement. This acid separates potassium from sodium.