Potassium Chloride (KCl)

What is Potassium Chloride?

Potassium chloride is a salt containing a bond between a metal and a halogen. It is denoted by the chemical formula KCl and is made up of potassium cations and chloride anions in a 1:1 ratio. It is characterized by a colourless, crystalline appearance and an odourless smell.

In its solid form, potassium chloride can be easily dissolved in water and the resulting KCl solution is said to have a salty taste. An illustration describing the structure of a KCl molecule is provided below.

Potassium Chloride

Structure of Potassium Chloride

The type of chemical bond that holds together the potassium and chlorine atoms in a potassium chloride molecule is an ionic bond. The electronegative chlorine atom accepts the 4s electron belonging to the potassium atom and an ionic attraction arises between the resulting K+ and the Cl ions.

Properties of Potassium Chloride

In the solid-state, KCl is readily soluble in many polar solvents, including water. The salt is ionized into the K+ cation and the Cl anions in these polar solvents. Some other physical and chemical properties of potassium chloride are discussed in this subsection.

Physical Properties

  • The crystals of potassium chloride are made up of face-centred cubic (FCC) unit cells.
  • The molar mass of KCl is 74.5513 grams/mol.
  • Its density in the solid, crystalline form is 1.984 grams per cubic centimetre.
  • The melting and boiling points of potassium chloride are 1040 K and 1690 K respectively.
  • At 0oC, 20oC, and 100oC, the solubility of KCl in water corresponds to 217.1 g/L, 253.9 g/L, and 360.5 g/L respectively.
  • Potassium chloride is highly soluble in alcohols but not soluble in ether (organic compounds with the formula R-O-R’).

Chemical Properties

  • Since potassium chloride is completely ionized into K+ and Cl ions in water, the resulting aqueous solution exhibit high values of electrical conductivity.
  • The reduction of potassium chloride into metallic can be achieved with the help of metallic sodium, despite the lower electropositivity of sodium when compared to potassium.
  • This is achieved by heating the KCl with metallic sodium to a temperature of 850 o
  • The chemical equation for this reaction is: KCl + Na ⇌ NaCl + K

It can be noted that when the solid form of potassium chloride is subjected to a flame test, it burns with a pale violet or a lilac-coloured flame, as is the case with most other potassium-containing compounds.

Uses of Potassium Chloride

Potassium chloride has a wide range of medical and industrial applications. It is also an integral part of fertilizer production. Some important uses of KCl are listed below.

  • Potassium chloride is used in the manufacture of potash, an important form of fertilizer that enriches soils with potassium which promotes the growth of plant life.
  • The potash fertilizers made from KCl (called Muriate of Potash, or MOP) make up the majority of potash fertilizers sold worldwide.
  • The medical treatment of low blood pressure commonly employs potassium chloride as a part of the medication.
  • KCl is used as a salt substitute in food where a low concentration of sodium in the salt is desired in order to reduce the risk of high blood pressure.
  • Potassium chloride is one of the important raw materials required in the manufacture of potassium metal.
  • The metal halide salt KCl is also used in the manufacture of soaps. Water softening units can involve the use of potassium chloride as an alternative to sodium chloride as well.
  • The use of potassium chloride as a source of beta radiation is extremely useful in calibrating radiation monitoring equipment.
  • The flux required in the oxy-fuel welding of aluminium consists of potassium chloride along with the chloride salts of lithium and sodium.

Thus, the various physical and chemical properties of potassium chloride are discussed along with its uses. To learn more about potassium chloride and other potassium compounds such as potassium chlorate, register with BYJU’S and download the mobile application on your smartphone.

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