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Potassium Fluoride

Potassium fluoride, represented by the chemical formula KF, is an inorganic compound comprising an alkali metal potassium and monoatomic anion fluoride [1]. It exists in its solid state or aqueous solution form, with the mineral carobbiite being the naturally occurring KF [1]. It also exists in other compounds like potassium fluoride dihydrate (KFH4O2) and potassium fluoride tetrahydrate (KFH8O4) [1].

Potassium Fluoride Identification

CAS Number 7789-23-3 [1]
PubChem CID 522689 [1]
ChemSpider ID 23006 [2]
EC Number 232-151-5 [1, 3]
UNII 9082WG1G3F [1]
RTECS Number  TT0700000
InChI Key NROKBHXJSPEDAR-UHFFFAOYSA-M [1]

Potassium Fluoride Formula

How is Potassium Fluoride Prepared

It is synthesized by reacting potassium carbonate with excess hydrofluoric acid and then evaporating the subsequent solution to form potassium bifluoride crystals [4]. The crystals are then heated to produce potassium fluoride, as shown by the following equations [4]:

K2CO3 + 4HF → 2KHF2 + H2O + CO2

KHF2 → KF + HF↑

Reactions with Other Compounds

Silver Nitrate and Potassium Fluoride

If an aqueous solution of potassium fluoride is mixed with a solution of silver nitrate, a double displacement reaction occurs producing silver fluoride, as shown below [5]:

2KF + 2AgNO3 → 2KNO3 + 2AgF

Potassium Fluoride and Hydrobromic Acid

When potassium fluoride reacts with hydrobromic acid, it undergoes a double displacement reaction to form potassium bromide and hydrofluoric acid [6]:

KF + HBr → KBr + HF

Potassium Fluoride and Water

Reacting potassium fluoride with water causes it to completely dissociate wherein the fluorine ion mixes with water to produce hydrofluoric acid, and the potassium ions remain inactive as spectator ions. The ionic equation is as follows [7]:

F + H2O ↔ HF + OH

Potassium Fluoride Crystals

Properties and Characteristics of Potassium Fluoride

General Properties

Molar Mass/Molecular Weight 58.097 g/mol (anhydrous) [1, 3]

Physical Properties

Color and Appearance White/colorless deliquescent, crystalline powder [1]
Melting Point 858 °C, 1576 °F (anhydrous) [1, 3]
Boiling Point 1502 °C, 2741 °F [1]
Density 2.48 g cm-3 [1, 3]
State of matter at room temperature Solid [1, 3]
pH 8.5-10.3 at 25 °C [9]
Solubility Insoluble in alcohol but soluble in hydrogen fluoride [1]
Solubility in Water 102 g/100 ml at 25 °C, 92 g/100 ml at 18 °C [1]
Magnetic Susceptibility (χ) -23.6 X 10-6 cm3 mol-1 [8]

Atomic Properties

Crystal Structure Cubic

Potassium Fluoride Lewis Dot Structure

What Is It Used for

  • Salt fluoridation as a means of community-based fluoridation through the addition of KF to iodized salt, with fluoride concentration less than 250 mg per kg [1].
  • Preparing silver soldering flux used by crafters and metal workers [1].
  • Increasing the rate of chemical reactions as a catalyst in organic synthesis [1].
  • Etching and frosting glass because of the synthesis of soluble fluorosilicates [1].
  • Making disinfectants, insecticides, and pesticides [1].

Is It Safe

Ingestion or inhalation of excessive amounts of KF can cause acute toxicity [1]. Being highly corrosive, its contact with skin can result in severe burns [1]. Although it is non-combustible, it decomposes upon heating to yield toxic fumes [1].

References:

  1. Potassium Fluoride – Pubchem.ncbi.nlm.nih.gov
  2. Potassium Fluoride – Chemspider.com
  3. Potassium Fluoride – Americanelements.com
  4. Potassium Carbonate React with Hydrogen Fluoride – Chemiday.com
  5. Precipitation Reactions – Chem.libretexts.org
  6. Chemical Equation Balancer – En.intl.chemicalaid.com
  7. Write the net ionic equation for the equilibrium that is established when potassium fluoride is dissolved in water – Chemistryfeedsolutions.wordpress.com
  8. Magnetic Susceptibility Of The Elements And Inorganic Compounds – Gemstonemagnetism.com
  9. Potassium Fluoride – Hamptonresearch.com

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