Potassium Iodide Formula

Potassium Iodide

Potassium Iodide is one of the most common compounds used in Chemistry. This inorganic compound is white crystalline salt which is used in many fields like medicine, commercial and industrial applications. It is an ionic compound that is produced by treating potassium hydroxide (KOH) with iodine. It is soluble in water. It is used as a nutritional supplement in animal feeds and  in the human diet. The chemical formula of potassium iodide is KI and it participates in several important chemical reactions.

Potassium Iodide Chemical Formula

Potassium Iodide is a metal halide composed of potassium and iodine. (potassium and iodine formulae are K⁺ and I⁻ respectively. The bond between them is ionic. Potassium has an oxidation number of +1 and iodide has an oxidation number of -1, So, the formula for potassium iodide is KI.

The chemical formula for potassium iodide


Molar Mass

166.0028 g/mol


3.12 g/cm³

Melting Point

681 ⁰C

Boiling Point

1330 ⁰C


Soluble in water

Calculation of Molar Mass: The molecular formula of potassium iodide is KI, Potassium has an atomic weight 39.0983 and Iodine has an atomic weight 126.90447, Adding both of them we get: ( potassium iodine formula are K and I respectively)

126.90447 + 39.0983 = 166.0028.

Potassium Iodide can be produced in industries by treating KOH with iodine.

Structure of Potassium Iodide:

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Uses of Potassium Iodide:

  • It is a natural supplement for the human and animal diet.

  • It is added to certain salts so that iodine content is not lost during the oxidation process.

  • It is also helpful in protecting the body’s thyroid gland in the neck.

  • It is also used in photography, in the preparation of Silver Iodide.


Potassium Iodide (KI) is an important agent for protection against thyroid-related health effects. It is used with silver nitrate to make silver iodide (AgI), a chemical used in making film photography. Potassium Iodide is also used in organic synthesis mainly in the preparation of aryl iodides in the Sandmeyer reaction (Organic Chemistry).

Reactions Involving Potassium Iodide:

2CuSO₄ + 4KI → 2Cul + I₂ + 2K₂SO₄

2KI + Cl₂ → 2KCl + I₂

2KI + Br₂ → 2KBr + I₂ 

FAQs (Frequently Asked Questions)

Question: Is Potassium Iodide Chemically Electrically Neutral?

Answer: Potassium iodide is an ionic compound and the chemical formula potassium iodide is KI

It is electrically neutral because the formula KI has a net zero charge. (+1 + -1 = 0), it has equal amounts of positive and negative charge. Potassium forms a positive ion and iodine form a negative ion.

Question: What are Some Common Side Effects of Potassium Iodide (KI)?

Answer: Skin rashes, Swelling of the salivary glands, diarrhea, abdomen pain, headache.

An allergic reaction can have more serious symptoms which include fever and joint pains; swelling in some parts of the body (face, lips, tongue, throat, hands, or feet); trouble in breathing,  or swallowing, shortness of breath. Excess usage can also harm pregnant women.

Question: What will be Observed When:

(i) Potassium iodide is reacted with lead nitrate?

(ii) Identify the type of reaction involved.

(iii) Give a balanced chemical equation for the potassium iodide equation.


(i) When potassium iodide is added to aqueous lead nitrate,  potassium nitrate, and a precipitate of lead iodide is formed which is yellow in color.

The reaction involved is: Pb(NO₃)₂ + 2KI → PbI + KNO₃

(ii) The type of reaction involved is a double displacement reaction or precipitation reaction.

(iii) Balanced equation  Pb(NO₃)₂ + 2KI → 2PbI + 2KNO₃

(chemical formula potassium iodide is (KI))