[demonat0r]

Xe and F2 gasses are put into a chamber. The partial pressure of F2 is 8.0 atm while the partial pressure of Xe is 1.7 atm. After the reaction is complete, the partial pressure of pure F2 is now 4.6 atm and a solid is formed. What is the formula of that solid?
a) XeF2
b) XeF3
c) XeF4
d) XeF
e) XeF8

i have no idea how to do this problem and it was on my test. please help.

[macman104]

You can relate partial pressures to moles ratios.  Also, you can infer that because the question says "after the reaction is complete" and only the partial pressure of F₂ is given, that all of the Xe reacted. 

Can you figure out how to compute how much of everything reacted using that information?

[demonat0r]

oh ok so since 1.7 moles of Xe and (8.0-4.6 = 3.4) 3.4 moles of F2 reacted,
1.7 / 5.1 = .333
3.4 / 5.1 = .666

1/3 Xe and 2/3 F
so would the formula be XeF2?

[macman104]

Yup, or you can look at it like F having twice as much as Xe

[ARGOS++]

[macman104]

ARGOS, nice catch, thanks!  You are correct, it is F₂!

[ARGOS++]

Dear macman104;

But as I told:   So the correct formula will be a little different:  c.) XeF₄ and not XeF₂!

Good Luck!
                    ARGOS⁺⁺

[demonat0r]

Dear macman104;

But as I told:   So the correct formula will be a little different:  c.) XeF₄ and not XeF₂!

Good Luck!
                    ARGOS⁺⁺

ahhh thanks for the catch there!