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Potassium Hydroxide Formula

Last updated date: 23rd Apr 2024
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Caustic Potash Formula

This article primarily deals with the structural and chemical formula of potassium hydroxide. Potassium hydroxide or as it is commonly termed caustic potash is one of the most important inorganic compounds and just like sodium hydroxide (NaOH), it is also a prototype strong base. Due to the basic and caustic properties, it has vast applications in the Industries. Potassium hydroxide is one of the most important and only prosecutor in many liquid soap solutions as well as many potassium-based chemicals. Therefore in 2005, the total production of potassium hydroxide was about 700,000 to 800,000 tons. Thus it is very important to learn the potassium hydroxide formula (known commonly as caustic potash formula). It is one of the organic compounds that is having a vast range of applications in almost all chemical industries. 

Chemical Formula of Potassium Hydroxide

The potassium hydroxide formula, commonly known as caustic potash formula is represented as KOH. It is predominantly an ionic compound. If the caustic potash formula is broken into two components with one hydroxyl anion [OH\[^{-}\]] that has a single negative charge on it and potassium ion [K\[^{+}\]] with one positive ion, thus the charge ratio becomes 1:1 and thus one potassium ion makes a stable bond with one hydroxyl ion. The synthesis of potassium hydroxide is very similar to that of sodium hydroxide in the industrial process which is known as the chloralkali process. The process follows the electrolysis of potassium chloride that produces potassium hydroxide, which is the chemical name of caustic potash with the release of chlorine gas as a by-product. Now by looking at the chemical formula of caustic potash that is KOH, the K-O bond is ionic due to the high electronegativity but the O-H bond in this case is covalent even when the electronegative difference is high. It is because after making the ionic bond by charge transfer with potassium, oxygen possesses more negative charge and as charge separation requires a lot of energy thus the ionization of H-O is not possible as the first ionization with K-O already happened. It is because the second ionization needs more energy for charge transfer than the first ionization due to high charge density. therefore, in the chemical formula for potassium hydroxide the K-O bond is ionic but the O-H bond is covalent.

Structural Formula of Potassium Hydroxide 

The KOH molecule in its solid-state crystallizes at a higher temperature and form a similar structure to NaCl. The KOH crystallizes in the monoclinic space group of C\[_{2}^{2}\]ーP2\[_{1}\]. The dimension of the two molecules in a molecular cell is a = 3.95, b = 4.00, c = 5.75, 𝛃 = 103.6\[^{0}\]. The OH\[^{-}\] ion is an effectively spherical anion whose radius is measured equal to 1.53 Å that falls between Cl\[^{-}\] and F\[^{-}\] cations. This spherical radius is due to the randomly or rapidly disordered hydroxyl ion. At room temperature, where the hydroxyl (OH\[^{-}\]) ion is completely in order the K\[^{+}\] ion centres are distorted, thus making the KOH bond length (depending on the orientation of hydroxyl ion) ranging from 2.69 to 2.15 Å. Also, each of the potassium ion centres is surrounded by an octahedron of oxygen atoms that are distorted. The oxygen atoms form a zigzag chain on the plane of the b-axis and according to the advanced stoichiometric arrangement the hydrogen atoms either lie on or nearby the zigzag chain of oxygen atoms that is very close or exactly linear in nature. Thus breaking of this hydrogen bond will lead to the formation of KOH cubic structure at high temperature. Therefore the molecular formula of potassium hydroxide is structurally represented as follows. 

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The cubic structure of solid KOH is as follows.

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Properties of Potassium Hydroxide

Some of the important physicochemical properties of KOH are listed below.



Potassium hydroxide symbol


Molar mass

56.11 g / mol


White solid




2.044 g / cm\[^{3}\] at 20\[^{0}\]C

2.12 g / cm\[^{3}\] at 25\[^{0}\]C

Melting point

360 \[^{0}\]C or 680 \[^{0}\]F or 633 K

Boiling point

1327 \[^{0}\]C or 2421 \[^{0}\]F or 1600 K

Solubility in water

85 g/ 100 ml (-23.2 \[^{0}\]C)

97 g/ 100 ml (0 \[^{0}\]C)

121 g/ 100 ml (25 \[^{0}\]C)

138.3g/ 100 ml (50 \[^{0}\]C)

162.9 g/ 100 ml (100 \[^{0}\]C)


Soluble in glycerol, alcohol but insoluble in liquid ammonia as well as ether.

Solubility in alcohol

55 g/ 100 ml (28 \[^{0}\]C) in methanol

Approx. 14 g/ 100 ml (28 \[^{0}\]C) in isopropanol

Basicity (pK\[_{a}\]) value

-0.7 for KOH (aq)

Magnetic susceptibility

-22.0 x 10\[^{-6}\] cm\[^{3}\] / mol

Refractive index

1.409 at 20 \[^{0}\]C

Crystal structure


Heat capacity

65.87 J / mol K

Std. molar entropy

79.32 J / mol K

Std. enthalpy of formation

-380.2 J / mol K


  1. KOH is used as an electrolyte in all the alkaline batteries

  2. By saponification, KOH is used for making solid as well as liquid soaps.

  3. Many of the potassium salts that are used in many industrial purposes are manufactured by reacting KOH.

  4. They are also used in chemical manufacturing, fertilizers production, petrochemical refining and cleansing solutions.

FAQs on Potassium Hydroxide Formula

Q1. What are the Hazards of KOH?

Ans. Sudden exposure to this chemical cause irritation in the eyes with redness and swelling. Exposure to this chemical for a long duration can cause burn and potential blindness. The repeated contact with the potassium dust or the dilute solution has major tissue-damaging effects.

Q2. What is an Alcohol Potash Compound?

Ans. An alcoholic potash formula is C2H7KOH which is known as potassium hydroxide ethanol or ethanol KOH. it is an ethanolic compound that has potassium hydroxide in ethanol solution.