How Does Potassium Cyanide Behave Chemically?
Potassium cyanide is a chemical compound with the formula KCN. This colorless crystalline salt, which will be similar in appearance to sugar, and is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications in our daily lives include making jewelry for chemical gilding and buffing.
Chemistry is really important and efficient for the research and study of living organisms because it helps students and scientists to understand the life processes of every living thing on earth at the molecular level. At any molecular level, every process of life takes place due to the involvement of various minor or major chemical reactions.
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More About Potassium Cyanide
A compound named potassium cyanide is a colorless crystalline salt, similar to sugar particles in its appearance. Its general formula is KCN and IUPAC's name is Potassium Cyanide. Potassium Cyanide is a very poisonous inorganic salt. Potassium Cyanide is a highly toxic substance in nature and exposure to this element can be very much lethal for humans. Apart from all these circumstances, it is considered to be highly soluble in water. Mostly it is used in the gold mining industries for the extraction of gold and silver ores. It is also used in various other industries for electroplating, fumigation, chemical gilding, and buffing.
Structure of Potassium Cyanide
Chemical Formula is KCN.
The molecular formula is KCN.
The molar mass of potassium cyanide is 65.12 g/mol.
Potassium cyanide is a compound formed of potassium( K+ cation ) and Cyanide (CN- anion). In which potassium is positively charged and cyanide is negatively charged ions. Carbon has a triple bond with the nitrogen ion. It is similar to the structure of NaCl crystalline solid.
Properties of Potassium Cyanide
Potassium Cyanide is a white crystalline colorless solid.
Its density is 1.52 g/ml.
Its melting point is 634.5’c
Potassium cyanide is highly soluble in water.
It decomposes slowly in the air and rapidly after heating.
Potassium Cyanide, when reacted with hydrogen peroxide, forms a less harmful cyanide derivative.
KCN+ H2O2 -> KOCN+ H2O
It is a toxic substance. It tastes bitter and it exhibits burning sensations.
Preparation of Potassium Cyanide
Potassium Cyanide can be prepared by various methods in industries as per their use. The most commonly used methods are:
When hydrogen cyanide is reacted with an aqueous solution of potassium hydroxide:-
HCN + KOH -> KCN + H₂O
When Formamide is reacted with KOH:-
HCONH2 + KOH -> KCN + 2H2O
Uses of Potassium Cyanide
Potassium Cyanide and Sodium Cyanide are widely used for the production of nitriles and carboxylic acids.
Potassium Cyanide was produced for the decomposition of potassium ferrocyanide. It was produced before the invention of the Castner process.
In the colloidal process, KCN is used as a photographic fixer.
It is used in the gold mining procedure, where KCN forms water-soluble Potassium gold cyanide and Potassium Hydroxide in the presence of oxygen.
4Au+ 8KCN +O2 +2 H2O -> 4KAu(CN)2 + 4KOH
KCN is used in mining industries of gold and other metals.
Potassium cyanide is used for the preparation of plastic and another organic synthesis.
It is used for electroplating and fumigation.
Potassium Cyanide is also used in warehouses.
It is also used as an insecticide by farmers.
KCN
Potassium cyanide is a highly toxic inorganic substance with the general formula KCN. It is generally prepared by the reaction of hydrogen cyanide (HCN) and potassium hydroxide (KOH). This is made up of a solid base (KOH) and a weak acid (HCN). This is used for the extraction of gold, silver, and other metals. It is one of the forms of cyanide prepared for the decomposition of potassium ferrocyanide before the invention of the Castner process.
Potassium Cyanide is harmful to health. If someone inhales this element then they may face severe health problems which can even lead to death. A person may also suffer from headaches, vomiting, dizziness, and seizures which can be harmful to human health.
Potassium cyanide is a salt prepared with the help of hydrogen cyanide or a reagent formamide.
FAQs on Potassium Cyanide: Structure, Properties, Preparation, Uses
1. What is potassium cyanide, and what is its chemical structure?
Potassium cyanide is a highly toxic inorganic compound with the chemical formula KCN. It is a salt composed of the potassium cation (K⁺) and the cyanide anion (CN⁻). Structurally, it forms a crystalline solid similar to sodium chloride. The cyanide ion itself has a linear structure, with a triple bond between the carbon and nitrogen atoms (C≡N⁻).
2. How is potassium cyanide typically prepared?
The most common method for preparing potassium cyanide involves a neutralization reaction. It is produced by treating hydrogen cyanide (HCN) with an aqueous solution of potassium hydroxide (KOH). The reaction is as follows:
HCN + KOH → KCN + H₂O
After the reaction, the resulting potassium cyanide salt is obtained by evaporating the water.
3. What are the key properties and primary dangers of potassium cyanide?
Potassium cyanide exhibits several distinct properties and is known for its extreme toxicity.
- Appearance: It is a white, crystalline, or granular solid, which is deliquescent (absorbs moisture from the air).
- Solubility: It is highly soluble in water.
- Toxicity: The primary danger of KCN is its high toxicity. When ingested or absorbed, the cyanide ion (CN⁻) binds to the iron atom in cytochrome c oxidase, an essential enzyme in mitochondria. This action blocks the final step of the electron transport chain, preventing cells from using oxygen for energy production, leading to cytotoxic hypoxia and rapid death.
4. What are the major industrial uses of potassium cyanide?
Despite its toxicity, potassium cyanide has several important industrial applications. Its major uses include:
- Gold Mining: It is used in the cyanide process to extract gold from low-grade ores by forming a water-soluble coordination complex, K[Au(CN)₂].
- Electroplating: It is used in electroplating baths for depositing thin layers of gold and silver onto other metals.
- Organic Synthesis: It serves as a key reagent for introducing a nitrile (-CN) group into organic molecules, which is a crucial step in manufacturing various pharmaceuticals, plastics, and other chemicals.
5. How does potassium cyanide (KCN) differ from sodium cyanide (NaCN)?
Potassium cyanide and sodium cyanide are chemically very similar and often used for the same purposes, such as gold extraction. The core differences are:
- Cation: KCN contains the potassium ion (K⁺), while NaCN contains the sodium ion (Na⁺).
- Molar Mass: Their molar masses are different (KCN ≈ 65.12 g/mol, NaCN ≈ 49.01 g/mol), which is a factor in stoichiometric calculations.
- Preparation: KCN is made with potassium hydroxide (KOH), whereas NaCN is made with sodium hydroxide (NaOH).
6. Why does reacting an alkyl halide with KCN yield a nitrile, but using AgCN yields an isonitrile?
This difference arises from the bonding nature of the cyanides and the behaviour of the cyanide ion as an ambidentate nucleophile.
- Potassium Cyanide (KCN) is predominantly ionic. In solution, it dissociates into K⁺ and CN⁻ ions. The nucleophilic attack on the alkyl halide occurs through the carbon atom of the cyanide ion, as the resulting C-C bond is more stable. This forms an alkyl nitrile (R-CN).
- Silver Cyanide (AgCN) is predominantly covalent. The silver-carbon bond does not break easily. Therefore, the nitrogen atom, with its available lone pair of electrons, acts as the nucleophile, attacking the alkyl halide to form an alkyl isonitrile (R-NC).
7. How exactly does potassium cyanide enable the extraction of gold from ore?
Potassium cyanide is central to the MacArthur-Forrest process for gold extraction. The process, known as cyanidation, involves leaching crushed gold ore with a dilute solution of KCN in the presence of atmospheric oxygen. The gold atoms (Au) are oxidized and react with the cyanide ions (CN⁻) to form a highly stable and water-soluble coordination complex, the dicyanidoaurate(I) ion, [Au(CN)₂]⁻. This complex is then separated from the solid rock and the gold is later recovered from the solution, typically by reacting it with a more reactive metal like zinc.
