# Can antimony pentafluoride be made by adding hydrogen fluoride to antimony trifluoride?

I was looking at how the strongest acid was made and I found something I did not understand. On the Wikipedia page for antimony trifluoride it shows the production of $$\ce{SbF3}$$ using $$\ce{HF}$$: $$\ce{Sb2O3 + 6 HF -> 2 SbF3 + 3 H2O}$$ The page also shows production of $$\ce{SbF5}$$ using $$\ce{F2}$$:
$$\ce{SbF3 + F2 -> SbF5}$$ However on the page for fluoroantimonic acid it shows production of:

$$\ce{SbF5 + 2 HF -> SbF6- + H2F+}$$

So my question is why the production of $$\ce{SbF5}$$ seems to require fluorine insted of hydrogen fluoride? And is it possible to use hydrogen fluoride to make $$\ce{SbF5}$$?

It can be prepared using hydrogen fluoride, in a double displacement reaction:

$$\ce{SbCl5 + 5 HF -> SbF5 + 5 HCl}$$

However, hydrogen holds onto fluorine more tightly than does antimony in $$\ce{SbF5}$$.

Consider the reverse of your proposed reaction, which is preferred energetically:

$$\ce{SbF5 + H2 -> SbF3 + 2HF}$$

• @EdV, sorry, I don't have that info. And, as you state, it's not something I'd try to measure. Does Derek Lowe have an article on SbF5, similar to this in his series Things I Won't Work With blogs.sciencemag.org/pipeline/archives/2010/02/23/…? – DrMoishe Pippik Jun 19 at 19:27
• @EdV, your welcome, but I have Wikipedia to thank. – DrMoishe Pippik Jun 19 at 21:17
• so my takeaway is keep your Antimony pentafluoride away from your hydrogen. – zenot fun Jun 20 at 2:37