In which temperature range does WF_6 melt?

In summary, the question asks about the temperature range in which ##[W^{+VI}F_{6}^{-I}]## will melt. Based on the electronegativity difference between the elements and the high lattice energy, it is likely to have a melting point over 1000 degrees Celsius. However, the Wikipedia page states that it is actually a gas. The geometry of WF6 is octahedral, with non-bonding orbitals of fluorine potentially leading to coulomb interactions between units. The dominant interactions between units will determine the lattice energy and therefore the melting point of the compound.
  • #1
H Psi equal E Psi
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Hi Everyone

I'm studying material Engineering and I'm currently preparing chemistry for the summer exams.

Now, there is an old exam question which I don't know how to solve:

"In which temperature range does ##[W^{+VI}F_{6}^{-I}]## melt?"

My solution:

Well, the 18-Electron rule is not fulfilled. There is no crystal field stabilization energy since there are no d-electrons and there are no Pi-backbonds. But:
The electronegativity difference is larger then 1.5. Wolfram is a hard acid and Fluor a hard base. The lattice-energy is very high because both compounds are in a high oxidation state and have a small atom radius (especially Fluor).

Based on this i would say ##[W^{+VI}F_{6}^{-I}]## has a melting-point over 1000 degrees Celsius.

I then looked it up on Wikipedia and it says that ##[W^{+VI}F_{6}^{-I}]## is a gas!?

How can one know this?
And is my train of thought correct? Because our professor ask this kind of question every time... He asked it once with ##OsO_{4}##, ##GeCl_{4}##,...

Thanks a lot for your help!
 
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  • #2
What is the geometry of WF6 and what does that tell you about its interactions?
 
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  • #3
TeethWhitener said:
What is the geometry of WF6 and what does that tell you about its interactions?

It's an octahedral crystal field. But I don't know what that tells me about its interactions :(
 
  • #4
H Psi equal E Psi said:
It's an octahedral crystal field. But I don't know what that tells me about its interactions :(
Right. So we know that WF6 is neutral and that it's an octahedron with W in the middle and F's completely surrounding the tungsten at each of the six vertices. With this geometry in mind, what do you think will be the dominant interactions when you bring two of these WF6 units close together?
 
  • #5
TeethWhitener said:
Right. So we know that WF6 is neutral and that it's an octahedron with W in the middle and F's completely surrounding the tungsten at each of the six vertices. With this geometry in mind, what do you think will be the dominant interactions when you bring two of these WF6 units close together?

I guess there will be coulomb interactions between the non-bonding orbitals of the fluorine?
 
  • #6
H Psi equal E Psi said:
I guess there will be coulomb interactions between the non-bonding orbitals of the fluorine?
The important thing to think of is: will there be significant interaction between the W of one WF6 unit and the F's of another WF6 unit? If yes, then this ionic interaction will dominate the lattice energy (by at least an order of magnitude). If no, then the lattice energy will consist chiefly of the weak dispersion interactions between the fluorines.
 
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1. What is the melting point of WF6?

The melting point of WF6 is 335°C (635°F).

2. At what temperature does WF6 turn from solid to liquid?

WF6 will melt at 335°C (635°F).

3. What is the melting behavior of WF6?

WF6 has a relatively high melting point of 335°C (635°F) and it turns from solid to liquid without any significant changes in its physical or chemical properties.

4. Can WF6 also exist in liquid or gaseous form at room temperature?

No, WF6 is a solid at room temperature and only melts at a temperature of 335°C (635°F).

5. What is the impact of temperature on the properties of WF6?

The melting temperature of WF6 is important for its use in various industrial processes, as it can affect its reactivity and stability. At higher temperatures, WF6 can also undergo sublimation, where it directly changes from solid to gas without melting.

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