Hydrocyanic Acid Formula: Structure, Properties, Uses

Hydrocyanic acid , also known as hydrogen cyanide (HCN), is a colorless liquid formed when hydrogen cyanide is dissolved in water. Its vapor, a characteristic bitter almond scent, is lighter than air and disperses quickly. This chemical compound is typically sold commercially as an aqueous solution containing 2 to 10% hydrogen cyanide. However, caution must be taken when handling this substance as both its solutions and gaseous form are highly toxic and can decompose into ammonium formate over time. Due to its hazardous properties, the storage and transportation of this transparent liquid are strictly prohibited.

Hydrocyanic Acid Formula and Structure

The chemical formula of hydrocyanic acid is HCN. The molecular formula of hydrocyanic acid is CHN. The molar mass is 27.03 g/mol. So, we can see that hydrogen cyanide is a simple planar molecule with a triple bond between the carbon and nitrogen atoms. Hydrogen isocyanide (HNC) is hydrocyanic acid's structural isomer (tautomer).

Occurrence

Cherries, apples, as well as apricots, contain small amounts of cyanohydrins that produce hydrocyanic acid in their pits.

Preparation

Hydrocyanic acid can be prepared on a laboratory scale by adding acids to the cyanide salts of alkali metals like the NaCN, KCN, and more.

HCl + NaCN → HCN + NaCl

In the industrial field, the main preparation of it is by the oxidation reaction of methane plus ammonia at around 1200 °C, over a platinum catalyst (Andrussow oxidation):

2 CH ₄ + 2 NH ₃ + 3 O ₂ → 2 HCN + 6 H ₂ O

Physical Properties

Hydrocyanic acid, for instance, has a pale blue color or is colourless transparent in liquid form (hydrogen cyanide), and hydrogen cyanide has no colour at all in gaseous form. A density of 0.687 g/mL is assigned to hydrocyanic acid. It boils a little above room temperature at 25.6 °C (78.1 °F). Furthermore, it has a very distinctive smell that reminds people of the presence of this extremely poisonous compound by smelling like bitter almonds.

Also Check – Charles Law Formula

Chemical Properties

If we talk about this acid’s strength, we see it is a very weak one which partially ionizes in water to give H+ (or H3O+) plus the cyanide anion, CN–.

HCN + H ₂ O → H ₃ O+ + CN ^–

It reacts with bases to make salts that we referred to as cyanides.

HCN + KOH → KCN + H ₂ O

Also Check – Molar Volume formula

Uses

However, HCN is an important substance, despite being very toxic. It's used to make a number of useful industrial chemicals, including sodium cyanide, potassium cyanide, methyl methacrylate (monomer used to make plastics and polymers), EDTA and NTA, as well as nylon, a polymer. In addition, HCN is also used to prepare pesticides and chemical warfare agents.

Also Check – Discovery of Proton Formula

Health Effects

As we know that HCN is a very toxic chemical. It is considered to be very lethal even if taken in a small dose. Even if only a hundred parts per million of hydrogen cyanide are present in the air, it will kill a human in less than one hour. Moreover, if anyone ingests it, they may die instantly. If it is present in high concentrations, it can also be very explosive.