Posted by Deanne on Sunday, January 9, 2011 at 4:49pm.
Part 1.
Take a 100 g sample which will give you 95 g F and 1 g H.
Convert to moles.
95/atomic mass F = 95/19 = 5
5/atomic mass H = 5/1 = 5
So the ratio is 1:1 and the formula is HF.
part 2. How much F do you have total (in UF6)? Convert 4.267 g UF6 to moles.
4.267/molar mass UF6. Convert that to moles F (multiply by 6), then convert moles F to grams F (multiply by atomic mass F). I get something like 1.4 but you should do it more accurately. Some of the F will be in the solid compound and some in the HF. How many grams in the HF. HF has a mass of 0.97, it has a 95% F; therefore, g F in HF is 0.97 x 0.95 = 0.9 (again you do it more accurately. Subtract from the 1.4 to determine amount F in the solid (about 0.5 or so). Then % in gas (HF) is (0.9/1.4)*100 = ??
% in solid is 100% - % in HF = ??
part 3.
I don't how you have been taught to do these but I do them, probably a little unconventional, this way.
moles UF6 = 4.267/352.02 = 0.010.012 or so. So 0.012 moles UO_{x}F_{y} will be formed. moles = grams/molar mass. You know moles and grams, solve for molar mass. I get something like 308. Subract 238 for U to leave 70. Subtract 1F and 1 O to leave 70-19-16 = 35. That looks like another O and another F (16+19) would do it so the formula should be UO2F2.
Part 4.
Use the percent you found in part 2 to help answer this, although you really don't need that. If you write
UF4 + H2O ==> UO2F2 + HF it's easy enough to balance as is. The percents, if you wish to use them, tells you that the HF is twice the F that is in UO2F2.