Hydrocyanic Acid consists of the elements Hydrogen, Carbon, and Nitrogen. Hydrogen is the lightest, colorless, odorless, tasteless, and flammable gas. Its atomic number is 1 and is represented by the symbol H. Carbon is a nonmetal present in group-14 of the periodic table. Its atomic number is 6 and is represented by the symbol C. Nitrogen is a colorless, tasteless, odorless gas and the most plentiful element in Earth’s atmosphere. It is present in group-15 of the periodic table and is represented with the symbol N.
Hydrocyanic Acid Formula
Hydrocyanic acid is a dangerous, highly volatile liquid with the chemical formula HCN. It was discovered by a Swedish chemist, Carl Wilhelm Scheele, in 1782. It is a liquid of hydrogen cyanide in water. The odor of Hydrocyanic acid is like the fragrance of bitter almonds. Its vapor is lighter than air and dissipates rapidly. Commercially, Hydrocyanic Acid is sold as an aqueous solution containing 2-10% hydrogen cyanide. Hydrocyanic Acid slowly decomposes to form Ammonium formate. Hydrocyanic Acid occurs naturally in the pits of some fruits like apples, cherries, and apricots.
Preparation of Hydrocyanic Acid
- In the laboratory, Hydrocyanic Acid is prepared by adding acids to cyanide salts of alkali metals such as NaCN, KCN, etc. The reaction of this given as-
HCl + NaCN ⇢ HCN + NaCl
- It is also prepared by the oxidation reaction between Methane and ammonia at 1200°C in the presence of a platinum catalyst.
2CH4 + 2NH3 + 3O2 → 2HCN + 6H2O
Structure of Hydrocyanic Acid
Hydrocyanic Acid Structure
Physical Properties of Hydrocyanic Acid
- Hydrocyanic Acid appears in colorless or pale blue color.
- The odor of Hydrocyanic Acid is a bitter almond odor.
- The molar mass of Hydrocyanic Acid is 27.0253 g/mol.
- The boiling point of Hydrocyanic Acid is 25.6°C.
- The melting point of Hydrocyanic Acid is -13.4°C.
- The density of Hydrocyanic Acid is 0.687 g/mL.
Chemical Properties of Hydrocyanic Acid
- Hydrocyanic Acid reacts with bases like Sodium hydroxide/ Potassium hydroxide to form Sodium cyanide/ Potassium cyanide.
HCN + NaOH ⇢ NaCN + H2O
HCN + KOH ⇢ KCN + H2O
- Hydrocyanic Acid is soluble in water and ethanol.
Uses of Hydrocyanic Acid
- Hydrocyanic Acid is used in electroplating and hardening of iron and steel.
- It is used to kill pests such as rodents in warehouses.
- Hydrocyanic Acid is used in the production of plastics, synthetic rubber, and acrylic fibers.
- It is used in the manufacturing of cyanide salts, dyes, and acrylonitrile.
- Hydrocyanic Acid is also used as a fumigant.
Sample Questions
Question 1: Is Hydrocyanic Acid a strong or weak acid?
Answer:
Hydrocyanic Acid is a weak acid because it has a strong conjugate base. Hydrocyanic Acid has CN– ion which is a very strong conjugate base.
Question 2: Find the molar mass of Hydrocyanic Acid?
Answer:
Hydrocyanic Acid consists of 1 Hydrogen, 1 Carbon and 1 Nitrogen atoms.
Atomic weight of Hydrogen atom = 1.00784
Atomic weight of Carbon atom = 12.01
Atomic weight of Nitrogen atom = 14.0067
Molecular weight of HCN = 1.00784 + 12.01 + 14.0067
= 27.02
Question 3: Is Hydrocyanic Acid is a hazardous compound?
Answer:
Hydrocyanic Acid is dangerous compound. It is poisonous and used as suicidal agent. On inhaling it causes headache, dizziness, feeling of suffocation, nausea, etc.
Question 4: What is the hybridization and shape of the compound HCN?
Answer:
The hybridization of carbon atom is sp hybridization. In the Hydrocyanic Acid there are two sigma bonds C-H and C-N and the number of sigma bonds in HCN are same as the number of hybrid orbitals formed. The molecular shape of Hydrocyanic Acid is linear.
Question 5: What are the uses of Hydrocyanic Acid?
Answer:
Hydrocyanic Acid is used in the production of plastics, synthetic rubber and acrylic fibres. It is used in manufacturing of cyanide salts and dyes. Hydrocyanic Acid is also used in mining, electroplating and synthesis of chemicals.
Question 6: What happens when Hydrocyanic Acid reacts with a base?
Answer:
Hydrocyanic Acid reacts with bases like Sodium Hydroxide to produce Sodium cyanide. The reaction of it is given below,
HCN + NaOH ⇢ NaCN + H2O