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Hydrocyanic acid is a water-based liquid containing hydrogen cyanide and its chemical formula is HCN. Hydrocyanic acid is a colorless liquid with a vapor that is lighter than air and evaporates quickly. It is typically sold as an aqueous solution containing 2 to 10% hydrogen cyanide. Hydrogen cyanide aqueous solutions slowly decompose to form ammonium formate.
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Key Terms: Hydrocyanic acid, Hydrocyanic acid uses, Ore Extraction, Physical properties of Hydrocyanic Acid, Chemical properties of Hydrocyanic Acid
What is Hydrocyanic Acid ?
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Hydrocyanic Acid is a highly poisonous colorless gas with a distinct bitter almond fragrance. Because it is a hazardous transparent liquid, its storage and transportation are prohibited.
It interferes with cellular oxidative processes, hydrogen cyanide is extremely toxic. Humans can tolerate 50–60 parts per million parts of the compound per million parts of air for an hour without suffering serious consequences, but exposure to 200–500 parts per million of air for a half-hour is usually fatal.
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Hydrocyanic Acid Detailed Video Explanation:
Hydrocyanic Acid
- The administration of a lethal dose of the compound gas is one method of inflicting execution and because of its toxicity, hydrogen cyanide is an excellent solvent for a variety of salts.
- Although the compound is stable in its pure form, it polymerizes quickly when exposed to substances such as ammonia or cyanide. These salts are used in ore extraction, electrolysis, and steel treatment.
- Organic compounds such as aldehydes and ketones combine to form cyanohydrins, which are used as intermediates in organic synthesizes.
- Hydrocyanic acid is also commonly known as: Prussic acid, acetonitrile, formonitrile
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Properties of Hydrocyanic Acid
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The properties of Hydrocyanic Acid on the basis of density, molar mass, Boiling point and melting point are-
| Parameters | Chemical |
|---|---|
| Chemical Name | Hydrocyanic Acid |
| Density | 687 kg/m3 |
| Molecular Weight/ Molar Mass | 27.0253 g/mol |
| Boiling Point | 25.6 °C |
| Melting Point | -13.4 °C |
| Chemical Formula | HCN |
Occurrence of HCN
HCN is found in small levels in the pits of various fruits like cherries, apples, and apricots, and the fruit pits contain cyanohydrins from HCN.
Preparation of HCN
On a laboratory scale, hydrocyanic acid is made by mixing acids with the cyanide salts of alkali metals such as NaCN, KCN, and others.
HCl + NaCN HCl= NaCl + HCN
The oxidation reaction of methane plus ammonia at around 1200 °C over a platinum catalyst (Andrussow oxidation) is the most common method of preparation in the industrial field:
2 CH4 + 2 NH3 + 3 O2 + 2 HCN + 6 H2O = 2 HCN + 6 H2O
Preparation of HCN
Physical properties of Hydrocyanic Acid (HCN)
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HCN has a pale blue color or is colorless and transparent (hydrogen cyanide). The density of hydrocyanic acid is 0.687 g/mL. It boils at 25.6 °C (78.1 °F), which is somewhat higher than room temperature. Furthermore, it has a distinct odor that is similar to bitter almonds and is utilized to detect the presence of this extremely toxic toxin.
Chemical Properties of Hydrocyanic Acid (HCN)
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When hydrocyanic acid combines with a base such as sodium hydroxide, sodium cyanide and water are formed. The chemical formula is shown below.
HCN + NaOH = NaCN + H2O
Potassium cyanide and water are formed when hydrocyanic acid interacts with potassium hydroxide. The chemical formula is shown below.
HCN + KOH + KCN + H2O
Uses of Hydrocyanic Acid
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- It is used to kill pests in places like warehouses, grain storage bins, greenhouses, and ship holds.
- It is used to make cyanide salts, acrylonitrile, and colors.
- It is used as a fumigant in the horticulture industry.
- It is a highly valuable precursor in the manufacture of a variety of compounds.
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Things to Remember
- Hydrocyanic acid is a water-based liquid containing hydrogen cyanide and its chemical formula is HCN.
- Hydrocyanic Acid is a highly poisonous colorless gas with a distinct bitter almond fragrance. Because it is a hazardous transparent liquid, its storage and transportation are prohibited.
- HCN has a pale blue color or is colorless and transparent (hydrogen cyanide).
- HCN is used to kill pests, make cyanide salts, acrylonitrile etc.
Previous Year's Questions
- The pH of a 0.1 M aqueous solution of NH4OH is : (Kb=1.0×10−5)
- The pH of a solution prepared by mixing 2.0 mL of HCl solution of pH 3.0 and 3.0 mL of NaOH of pH 10.0 is…
- The pH of D2O and H2O at 298 K is
- The pH of human urine is approximately..
- The pH of neutral water is 6.5,then the temperature of water is…
- The pH of succus entericus is
- The pH of tears coming out of a person's eye is approximately
- The pH range for phenolphthalein is
- The pH value of 0.001 M aqueous solution of NaCl is
- The pH value of N/10 NaOH is
- The pKa of acetylsalicylic acid (aspirin) is 3.5.The H of gastric juice in human stomach is about 2.3 and the pH in the small intestine is about 8. Aspirin will be
- What is the correct increasing order of Bronsted bases?
- Which of the two acids form anhydrides? (I) Oxalic acid (II) Succinic acid (III) Benzoic acid (IV) Phthalic acid
- The sequence of acidic character is...
Sample Questions
Ques 1.What is HCN Molecular Geometry, and how does it work? (3 marks)
Ans. HCN has a linear molecular geometry. The A, X, and Notation theories can also be used to verify appropriate molecular geometry. The core carbon would be A, the number of atoms linked to it would be X (in HCN, there are two – Hydrogen and Nitrogen), and the number of lone pair electrons or nonbonding electron pairs would be N
Ques 2. What is the polarity of the HCN bond? (3 marks)
Ans. There are situations of polarity when the electronegativity of the atoms differs. When dealing with sophisticated molecules, it's vital to think about the chemical contradictions that result from combining all of the single bond polarities. The magnitude of the vector will not be zero if there are two atoms that are not identical, and the bond will not be polar. Hydrogen cyanide is a linear substance. Carbon has a higher electronegative potential than Hydrogen. As a result, there is a vector from hydrogen to coal. Furthermore, because nitrogen is more electronegative than carbon and even hydrogen, a bond vector is suggested.
Ques 3. What color does HCN come in? (1 mark)
a) Dark green
b) Yellow
c) The color red
d) Colorless or pale blue
Ans. ( D ) Colorless or pale blue
Explanation- The natural color of Hydrocyanic Acid is colorless or pale blue
Ques 4. What are the Health Effects of Hydrocyanic Acid? (3 marks)
Ans. HCN is a highly hazardous substance. Even in modest doses, it is regarded to be extremely dangerous. It will kill a human in less than an hour, even if only a few hundred parts per million of hydrogen cyanide are present in the air. Furthermore, anyone who ingests it may die instantly. Furthermore, if it is present in large amounts in the air, it can be quite explosive.
Ques 5. What is the molecular shape of HCN? (1 mark)
Ans. The molecular shape of Hydrocyanic Acid is linear.
Ques 6. What is the hybridization of HCN? (2 marks)
Ans. In HCN structure the hybridisation of carbon atoms is sp hybridisation. There are two sigma bonds, C-H and C-N. The number of sigma bonds is equal to the number of hybrid orbitals formed.
Ques 7. Is HCN a strong or weak acid? (1 mark)
Ans. Hydrocyanic Acid Is a weak acid. A weak acid always has a strong conjugate base. CN- is a strong conjugate base here in Hydrocyanic Acid.
Ques 8. What is HCN bond polarity? (2 marks)
Ans. In different electronegativity in atoms, there are cases of polarities. When the molecules are complicated, it becomes necessary to consider the expectations of molecular contradictions that are born from the combination of the single bond polarities. When there are two atoms, and both of them are not identical, the magnitude of the vector will not be zero, and the bond will not be polar.
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