[crazycow1]

water is added to 4.267 grams f UF6. the only products are 3.730 grams of a solid containing only uranium, oxygen and fluorine and 0.970 grams of a gas. the gas is 95.0% fluorine, and the remainder is hydrogen.


from these data, determine the empirical formula of the gas.
What fraction of the fluorine of the original compound is in the solid and what fraction in the gas after the reaction?
what is the formula of the solid product?

[kingchemist]

The empirical formula of the gas is easy to work out by considering 95.0% of 0.970g for F and 5.0% of 0.970g. I am using F=19, H=1, U=238, O=16

Element                                H                                 F                    
Mass (g)                           0.0485                         0.9215
Moles                              0.0485 /1                     0.9215/19
Ratio                                0. 0485                        0.0485
divide by smallest                 1                                   1
                                                        HF

UF6 = 238 +19x6 = 238+114 = 352g/mol
352g UF6 contain 114 g F
4.267g ..    ...      (114/352) x 4.276 = 1.382g F
So there was 1.382g of F at the start

So if 0.9215g of F ended up in HF, this is 0.9215/1.382 = 0.667  ( 2/3 rds)
Fraction in solid = (1.382-0.9215)/1.382 = 0.333 (1/3 rd ) ends up in the solid.

352g UF6 contain 234 g U
4.267g ..    ...      (234/352) x 4.276 = 2.837g U

This ends up in the solid product. So it contains 2.837g U and  (1.382-0.9215) = 0.4605g F
If the solid product weighs 3.730g, it must contain 3.730 - (2.837 + 0.4605) = 0.4325g of oxygen

Element                                U                                 F                               O                  
Mass (g)                           2.843                            0.4605                      0.4325
Moles                           2.843 /234                     0.4605/19                     0.4325/16
Ratio                               0.0121                        0.0242                        0.0270
divide by smallest                 1                                   2                           2.23


Just check through the calculation as 2.23 seems odd. However formula might not be UF2O2 but U4F8O9

I was googling to find a possible formula but found this solution to what looks like the same problem a year ago.
http://answers.yahoo.com/question/index?qid=20080812115927AAIxu5Y

Also found after I had done all the work
UF6 + 2 H2O= UO2F2 + 4 HF
hey