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Aluminium Fluoride Formula – Structure, Properties, Uses, Sample Questions

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  • Last Updated : 16 Jun, 2022
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Aluminum fluoride is most commonly found as a hydrate. Furthermore, this hydrate contains one or more water molecules. Moreover, in the most prevalent of these hydrates, there are seven molecules of water for every two aluminum fluoride molecules in a crystal. Above all, this chemical is helpful in the production of pure aluminum. 

Aluminium Fluoride Formula

Aluminum fluoride is a colorless chemical compound having the molecular formula AlF3. It is primarily utilized in the production of aluminum. It can be found in nature as oskarssonite and rosenbergite. It can also be manufactured. The vast majority of aluminum fluoride is produced by heating hydrogen fluoride with alumina or aluminum oxide to 700 °C.

Chemical Formula: The formula of aluminium fluoride is AlF3.

Structure of Aluminium Fluoride 

 

Physical Properties of Aluminium Fluoride 

  • Aluminum fluoride has the appearance of white powder or granules. Furthermore, aluminum fluoride has an odorless property. Furthermore, this combination is denser than water.
  • At a temperature of 25°C, its solubility in water is approximately.559g/100 mL.
  • Furthermore, this molecule is very marginally soluble in alkalis and acids.
  • Even highly concentrated acid has less effect on Aluminium fluoride
  • Aluminum fluoride has a very high melting point of 1291 degrees Celsius.
  • At 1238 °C, its vapor pressure is 1 mm.
  • As compared to trialkylaluminiums, the chemical is less vulnerable to oxidation.
  • In nature, aluminum fluoride is non-flammable.
  • When this chemical reaches the point of breakdown, it generates very hazardous hydrogen fluoride vapors.
  • Aluminum fluoride sublimates at a high temperature of 1272 °C and a pressure of 760 mmHg. 

Chemical Properties of Aluminium Fluoride 

Experts are aware of many hydrates of aluminum fluoride in addition to AlF3. Furthermore, with the formula AlF3.  xH2O, these compounds comprise monohydrate x = 1, two polymorphs of a trihydrate x = 3, hexahydrate x = 6, and x = 9 nonahydrate. Most aluminum fluoride is generated by processing alumina with hydrogen fluoride. Furthermore, this occurs at a temperature of 700 °C. Fluorosilicic acid may be used to make aluminum fluoride.  Alternatively, ammonium hexafluoroaluminate can be thermally decomposed to produce aluminum fluoride. 

Uses of Aluminium Fluoride 

  • Aluminum fluoride is primarily used as an additive in the manufacturing of aluminum and in electrolysis.
  • Some intriguing discoveries have revealed that aluminum fluoride has a wide range of applications in a number of sectors and activities. It is, for example, a key component in the manufacture of fluoroaluminate glass.
  • Fluoroaluminate glass is used in a variety of optical fiber applications, including medical and fiber-optic imaging.
  • Aluminum fluoride is widely used in ceramics, where it is the primary chemical constituent for final goods. 

Sample Questions 

Question 1: Why is aluminum fluoride ionic?

Answer: 

Aluminium fluoride is classified as an ionic compound due to the larger electronegativity gap between the two atoms that comprise the complex. 

Question 2: In a single formula unit, how many electrons are transported between aluminum and fluoride?

Answer: 

In the formation of the ionic compound aluminium fluoride, aluminium contributes three outer electrons to three fluorine atoms, resulting in a triple positive aluminium ion and three single negative fluoride ions. 

Question 3: Why is the melting point of aluminum fluoride so high?

Answer: 

The melting point of aluminium fluoride is higher than that of aluminium chloride. This is due to its ionic character, as compared to Aluminium Chloride’s covalent character. The cation in both compounds is the same, but the anion size varies. 

Question 4: Why is aluminum iodide covalent when aluminum fluoride is ionic? 

Answer: 

Aluminium iodide is covalent because the electron pair is easily driven away from the iodide ion,  Aluminium fluoride, on the other hand, is ionic because the alumnium ion cannot adequately polarise the tiny fluoride ion to create a covalent bond.

Question 5: Is aluminum fluoride water soluble?

Answer: 

Aluminum fluoride, Trihydrate is water soluble but insoluble in most organic solvents, whereas Aluminum fluoride, Anhydrous is insoluble in water. Aluminum fluoride is primarily used as an additive in the production of aluminium and by electrolysis. 

Question 6: Why is AlCl3’s melting point lower than AlF3‘s?

Answer: 

AlF3 has a higher melting point than AlCl3 because it is an ionic compound, whereas AlCl3 is a covalent compound with a polar covalent bond. Ionic compounds have a higher melting point than covalent ones because ionic bonds are stronger than covalent bonds. 

Question 7: What kind of bond would aluminum and fluoride form?

Answer: 

In the ionic compound aluminium fluoride, the aluminium donates its three outer electrons to three fluorine atoms, resulting in a triple positive aluminium ion and three single negative fluoride ions in terms of electron arrangement. 

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