How Does Potassium Iodide Work in Chemical Reactions?
What is Potassium Iodide (KI)?
Potassium iodide is described as an inorganic chemical compound which is denoted by the chemical formula - KI. This compound is defined as a metal-halide salt featuring an ionic bond between potassium cation (K+) and iodide anion (I–). This compound is colorless to white, and it appears as cubical crystals or white or powder granules. It has a saline taste and is highly bitter.
This compound is prepared using iodine and mixing potassium hydroxide. It is also one of the safe and most effective medicines required in a health system, and it is on the list of the World Health Organization of Essential Medicines.
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Potassium Iodide Structure (KI Structure)
A potassium iodide molecule contains one iodide anion and one potassium cation, which are held together with an ionic bond. The structure of a Potassium Iodide molecule can be illustrated below.
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Properties of Potassium Iodide
Let us look at the properties of Potassium Iodide below:
Physical Properties of Potassium Iodide
Chemical Properties of Potassium Iodide
Potassium iodide compound can be oxidized into an I2 molecule by introducing an oxidizing agent to it. One of the examples of such a reaction is given below:
2KI + Cl2 → 2 KCl + I2
This compound can be used as an iodide source in many organic synthesis reactions. One such example is given as the synthesis of aryl iodides from the arene's diazonium salts.
Benefit of Taking Potassium Iodide Compound During a Radiological Accident
It is assumed that the 'accident' produces notable amounts of iodine's radioactive isotopes (such as I-131 and I-125), and those get into the supply of food. They would then enter into the body and be taken up by the thyroid gland, which would become non-functional or cancerous.
By taking the KI compound, the thyroid gland would become saturated with Iodine, and for a while, quit taking up new (which is radioactive) Iodine. And then the thyroid gland would be saved.
Also, it is not completely clear how this would normally take place and whether it would be much useful to that of a fart in a whirlwind.
First, the radio-Iodine injury would take place slowly, and if the medical facilities still existed, treatment is available for the injury correction. Also, many do not know how many people would experience this specific injury mode.
And also, it does not do anything for the people exposed to radio-cesium, Strontium-90, and more related.
Saturated Potassium Iodide Solution
A saturated solution is defined as a solution that contains a similar amount of potassium iodide salt as would be in equilibrium with undissolved salt. It means this is a solution that we represent by the equilibrium.
KI(s) ⇌ K++I−
Uses of Potassium Iodide
Let us discuss the use of potassium iodide as follows:
Medical Uses
Dietary Supplement
Potassium iodide can be used in the human diet and also as a nutritional supplement in animal feeds. It is the most common additive for the latter used to "iodize" table salt (which is a public health measure to prevent iodine deficiency in populations that get little seafood). Also, iodide oxidation causes a slow loss of iodine content from the iodized salts exposed to excess air.
Thyroid Protection
Thyroid iodide compound uptake blockade with potassium iodide can be used in nuclear he medicine scintigraphy and some radioiodinated compound therapy that are not targeted to the thyroid, like iobenguane (MIBG), which can be used either to image or treat the iodinated fibrinogen or neural tissue tumors, which is used in the fibrinogen scans in clotting investigation. These compounds consist of iodine, but not in the form of iodide.
Nuclear Accidents
The U.S. Food and Drug Administration, in 1982, has approved potassium iodide to protect thyroid glands from radioactive iodine by involving fission emergencies or accidents. In an accidental attack or event in nuclear bomb fallout or on a nuclear power plant, volatile fission product radionuclides can be released. Out of these products, 131 (Iodine-131) is the most common and is specifically much dangerous to the thyroid gland since it can lead to thyroid cancer.
Side Effects of Potassium Iodide
There is a reason for caution by prescribing the ingestion of a high dose of iodate and potassium iodide, as their unnecessary usage can cause conditions like the trigger, Jod-Basedow phenomenon, and/or hypothyroidism and worsen hyperthyroidism, and then causes either temporary or even permanent thyroid conditions. Also, it can cause sialadenitis (which is an inflammation of the salivary gland), rashes, and gastrointestinal disturbances. Also, potassium iodide compound is not recommended for people having hypocomplementemic vasculitis and dermatitis herpetiformis - conditions that are linked to iodine sensitivity risk.
FAQs on Potassium Iodide (KI): Structure, Properties & Applications
1. What is potassium iodide and what are its key properties?
Potassium iodide is an inorganic ionic compound with the chemical formula KI. It consists of potassium cations (K⁺) and iodide anions (I⁻) held together by ionic bonds. It is a white crystalline salt that is highly soluble in water. Key properties include:
- Appearance: A white, crystalline solid at room temperature.
- Solubility: Highly soluble in water, and also soluble in ethanol and glycerol.
- Molar Mass: Approximately 166.00 g/mol.
- Melting Point: 681 °C.
- Chemical Nature: It acts as a source of iodide ions and can function as a mild reducing agent. When exposed to air and moisture over time, it can slowly oxidise to form potassium carbonate and elemental iodine, giving older samples a yellowish tint.
2. What are the most common uses of potassium iodide in chemistry and daily life?
Potassium iodide (KI) has several important applications, ranging from nutrition to industrial chemistry. Its primary uses include:
- Iodised Salt: It is the most common additive to table salt to prevent iodine deficiency, which can lead to thyroid problems like goitre.
- Analytical Chemistry: In iodometry, KI is used to react with oxidising agents to liberate iodine, which is then titrated. This is a common method for quantitative analysis.
- Organic Synthesis: It serves as a source of the iodide nucleophile in reactions like the Finkelstein reaction to prepare alkyl iodides.
- Medical Applications: Used as an expectorant, an antiseptic, and to protect the thyroid gland from absorbing radioactive iodine in a nuclear emergency.
3. Why is the chemical formula for potassium iodide KI, and not K₂I or KI₂?
The formula is KI because it reflects the principle of charge neutrality in an ionic compound. Potassium (K) is an alkali metal (Group 1) and loses one electron to form a stable cation with a +1 charge (K⁺). Iodine (I) is a halogen (Group 17) and gains one electron to form a stable anion with a -1 charge (I⁻). To form a neutral compound, one K⁺ ion balances the charge of one I⁻ ion. Therefore, they combine in a 1:1 ratio, resulting in the formula KI. Formulas like K₂I or KI₂ would represent electrically imbalanced and unstable compounds.
4. What happens when an aqueous solution of potassium iodide reacts with lead(II) nitrate?
When a clear, colourless aqueous solution of potassium iodide is mixed with a clear, colourless solution of lead(II) nitrate (Pb(NO₃)₂), a double displacement reaction occurs. This results in the immediate formation of a bright yellow precipitate of lead(II) iodide (PbI₂). The other product, potassium nitrate (KNO₃), remains dissolved in the solution. The balanced chemical equation for this reaction is: 2KI(aq) + Pb(NO₃)₂(aq) → PbI₂(s) + 2KNO₃(aq). This reaction is a classic example used to demonstrate precipitate formation.
5. How is potassium iodide typically prepared in a laboratory setting?
A common laboratory method for preparing potassium iodide involves the reaction of an alkali, potassium hydroxide (KOH), with iodine (I₂). The process typically involves treating a hot aqueous solution of potassium hydroxide with iodine. This reaction forms both potassium iodide (KI) and potassium iodate (KIO₃). The potassium iodate is then reduced to potassium iodide, often by heating the mixture with carbon powder. The final product can be purified through crystallisation. The initial reaction is: 6KOH + 3I₂ → 5KI + KIO₃ + 3H₂O.
6. How does potassium iodide demonstrate its properties as a reducing agent?
Potassium iodide acts as a reducing agent because its iodide ion (I⁻) can be easily oxidised (lose an electron) to form elemental iodine (I₂). The oxidation state of iodine changes from -1 in I⁻ to 0 in I₂. A classic example is its reaction with an oxidising agent like acidified potassium permanganate (KMnO₄). The purple permanganate ion is reduced, losing its colour, while the colourless iodide ion is oxidised to form a brown solution of iodine. This ability to donate electrons makes KI a useful mild reducing agent in many chemical transformations.
7. What is the difference between potassium iodide (KI) and elemental iodine (I₂)?
While both involve the element iodine, they are chemically distinct substances with different properties:
- Composition: Potassium iodide (KI) is an ionic compound made of potassium and iodine ions. Elemental iodine (I₂) is a diatomic molecule consisting of two iodine atoms joined by a covalent bond.
- Appearance: KI is a white crystalline solid. I₂ is a greyish-black solid with a purple vapour.
- Solubility: KI is very soluble in water. I₂ is only slightly soluble in water but dissolves well in KI solution (forming the triiodide ion, I₃⁻) and in organic solvents like ethanol.
- Role: KI is a source of iodide ions, whereas I₂ acts as an oxidising agent itself.
