Percentage composition of NaF and AlF3 in Na4AlF6

[danne89]

Hi! How many per cent of NaF and AlF3 does Na4AlF6 consist of?

I get 20 % NaF, but that isn't correct. I've done such problems before, just this seems to be unusual. Can you maybe check my work.

Greatfull,
Danne

 

[dextercioby]

Question:What is the structure (geometry and bonding) and oxydation numbers of this hexafluoroaluminate of sodium
$$Na_{4}AlF_{6}$$

Daniel.

 

[danne89]

$$4 Na^-~ Al^{3+} ~ 6F^-$$
So the bonding between the F's and the Al is covalent. And the bonding between the Na's and the other group is ionic.

How do you write oxydation numbers in Latex? Anyway, it looks like this, I think:
Na_4 - -4
Al - +3
F_6 - -6

It can't be correct, though, for the numbers must equals zero.

 

[dextercioby]

Yes,that's what i was insinuating.The compound doesn't exist as a molecule (it's not neutral).Therefore it makes no sense to discuss its "concentration" of other molecules...

Daniel.

 

[danne89]

Spooky. I'll look it over some more times.

 

[Gokul43201]

I suspect, your original compound is cryolite ($Na_3AlF_6$), which is commonly used in the molten form for the electrolytic production of Aluminum.

$$Na_3AlF_6 \equiv 3NaF + AlF_3$$

PS : Na has oxid state = +1