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Barium Fluoride is a compound which consists of a positively charged Barium atom and two negatively charged Fluoride atoms, hence, the molecular formula BaF2. It is a colourless compound which occurs in nature as frankdicksonite in the form of solid. The Barium ion and the Fluoride ions form an ionic bond with each other. Under basic conditions, Barium Fluoride will adopt the structure of fluorite and at high pressure, it forms PbCl2 structure. This compound is mainly used in aluminium metallurgy, in producing welding agents as well as in enamel and and glazing fruits production. Barium Fluoride is also very sensitive to thermal shock and is insoluble in water.
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Barium Fluoride
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Barium Fluoride is a chemical compound having the formula BaF2. The IUPAC name of it is barium (2+) difluoride. The two Fluoride ions are ionically attached to one Barium ion as depicted in the image below:
Structure of Barium Fluoride
General Properties of Barium Fluoride
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The general properties of Barium Fluoride are:
- Barium Fluoride gives off the appearance of white cubic crystals.
- The refractive index of this compound is about 1.46 over the range of 700 nm to 5 µm.
- The melting and boiling point of BaF2 are 1,368 °C and 2,260 °C respectively.
- The density of Barium Fluoride is 4.89 g/cm³ whereas its molar mass is 175.34 g/mol.
- It is partially soluble in water.
- It’s longer exposure to moisture can degrade the transmission of its UV range.
- BaF2 can get corroded due to moisture but in a dry environment, it can be used till 800 oC.
Optical Properties of Barium Fluoride
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The optical properties of BAF2 are:
- It appears transparent when observed from the UV to infrared range ranging from 150 – 200 nm to 11 – 11.5 µm.
- It is a common and fast scintillator used for the detection of X-rays, gamma rays or high energy particles. Unlike most scintillators, Barium Fluoride possesses a unique property of not emitting ultraviolet light.
- It can also detect high energy neutrons by using the pulse shape discrimination techniques.
Gas Phase Structure of Barium Fluoride
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The gas phase structure of Barium Fluoride is described below:
- It is non-linear in the vapour form with a F-Br-F angle with approx 108 degrees.
- It also violates the VSEPR theory. The reason for this is that the D orbitals in the shell below the valence shell contribute to the cause.
- Another theory that is proposed is that the electron core polarisation of the core of the electron of the barium atom makes tetrahedral charge distribution interacting with the Ba-F bond.
Uses of Barium Fluoride
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The uses of Barium Fluoride are:
- It is used as a pre-opacifying agent.
- It is also used in enamel and glazing frits production.
- It is used in the production of welding agents. It is a component of coatings for welding rods and in welding powders.
- It is also extensively used in metallurgy, as a molten bath for refining aluminium.
- It is primarily used in windows for infrared spectroscopy. This has the use in the field of fuel oil analysis.
- It is also extensively used in optical instruments
Things to Remember
- The molecular formula of Barium Fluoride is BaF2 and occurs in nature as a solid and colourless compound.
- The bond between the atoms is ionic and is primarily insoluble in water.
- It has a white cubic crystal appearance.
- The refractive index is about 1.46.
- It appears transparent when viewed from UV or infrared range
- It can detect high energy neutrons using the pulse shape discrimination techniques.
- It is non-linear in vapour form and violates VSEPR theory.
Solved Questions
Ques. Can a precipitate of barium fluoride form when we mix 100 mL of 1.0 x 10-3 M Ba(NO3)2 and 200 mL of 1.0 x 10-3 M KF(aq) Ksp BaF2 = 1.0 x 10-6? (5 marks)
Ans. From given condition, we can conclude that
Total Volume = 300 mL
Also,
BaF2 = Ba+2 + 2F-
Ksp = [Ba+2] [F-]2
Also, Ba(NO3)2 = Ba+2 + 2NO3-
Ba(NO3)2 = 300 / 100 x 10-3 M = 3.33 x 10-4 M
Concentration of KF = 10-3 x 200 / 300 = 6.6 x 10-4 M
Ionic Product = (3.33 x 10-4) x (6.6 x 10-4)2 = 1.48 x 10-10
Since, Ksp is greater than Ionic Product, hence, no ppt is formed.
Ques. Barium fluoride is often used in glass manufacturing. Which of these is the correct formula and bonding type for barium fluoride? (2 marks)
- BaF, ionic
- BaF, covalent
- BaF2, ionic
- BaF2, covalent
- Ba2F, ionic
Ans. 3) BaF2 , ionic.
Explanation: It is one of most resistant optical fluorides out of all the others present in the market, hence it is used in the glass manufacturing industry in the ionic form.
Ques. What is the formula for barium fluoride? (3 marks)
Ans. Barium Fluoride is an ionic compound made up of an alkaline metal and a nonmetal. They are insoluble in water. The symbol of Barium is Ba and it belongs to group 1 and hence possesses a +2 cationic charge whereas fluorine is a non-metal having a charge of -1. So, by calculating the charges we get,
(+2) + (−1) = +1.
Hence, by Criss cross method, (Ba2+)(F−)2, charge is balanced as (1 × (+2) ) + (2 × (−1) ) = 0 .Hence the formula is BaF2.
Ques. What is an ionic compound? (2 marks)
Ans. Ionic compound is a compound made up of ions held together by electrostatic forces which is called the ionic bonding. The compound is completely neutral consisting of anion which is positively charged and cation which is negatively charged.
Ques. The solubility of the chemical compound barium fluoride i.e. BaF2, is 3.15 x 10-3 M at 25 °C. Calculate the solubility product and Ksp. (5 marks)
Ans. The dissociation reaction is as follows-
BaF2(s) ↔ Ba+ (aq) + 2 F- (aq)
In the reaction it is evident that for every single mole of BaF2 that is dissolved 1 mole of Ba+ and 2 moles of F- as a result. Thus calculating the solubility -
[Ba+] = 7.94 x 10-3M
[F–] = 2 [Ba+]
Ksp = [Ba+] [F–]2, Ksp = ([Ba+]) (2 [Ba+])2
Ksp = 4 [Ba+]3
Ksp = 4 (7.94 x 10-3M)3
Ksp = 4 (5 x 10-7)
Ksp = 2 x 10-6
The solubility product of barium fluoride (BaF2) is 2 x 10-6.
Ques. What are the uses of Barium Fluoride compound? (2 marks)
Ans. Barium Fluoride finds use in metallurgy, as a molten bath for refining. It is also used in the production of welding agents and pre opacifying agents.
It is also used in optical instruments and in windows for infrared spectroscopy and fuel oil analysis.
Ques. Is BaF2 an ionic or covalent compound? (2 marks)
Ans. Barium Fluoride is an ionic compound because it is made up of Barium cation, which has a +2 charge and Fluoride anion, which has a -1 charge. The compound has a molecular formula of BaF2. Since there is no shared bonding and only a transfer of ions, it is called an ionic bond.
Ques. What is the valency of fluorine atoms? (3 marks)
(a) 7
(b) 1
(c) 3
(d) 6
Ans. (b) 1
Explanation: Valency refers to the parameters by which one can measure the ability of an atom whether it is formed from a bond or a compound. The electronic configuration of fluorine (atomic number = 9) is 1s2 2s2 2p5. So we see that 2p only needs 1 electron to complete its valency. Hence the valency of fluorine is 1. Due to addition of a negative charge, fluorine is a negatively charged element.
Ques. Is Barium Fluoride soluble in water? (2 marks)
Ans. Barium Fluoride is a colourless, odourless crystal or white powder that is only slightly soluble in water solution. The solution it is otherwise soluble in is ethanol and methanol. The solubility of it in water is 1.58 g/L (10 °C) 1.61 g/L (25 °C) while the solubility product is 1.84 × 10−7.
Ques. Is Barium Fluoride a salt? (2 marks)
Ans. Yes, Barium Fluoride is a salt. It consists of Barium (Ba) and Fluorine (F) and it gives off a white appearance when powdered. It is otherwise colourless and appears transparent.
It is present as the mineral frankdicksonite in nature and it is a solid occurring element.
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