A compound of chlorine and fluorine, ClFn, reacts at about 75oC with uranium metal to produce uranium hexafluoride, UF6 and chlorine monofluoride, ClF (g). A quantity of uranium produced 3.53g UF6 and 343 mL ClF at 75oC and 2.50 atm. What is the formula (n) of the compound?

Answer 1

Use PV = nRT to caluclate mols ClF from the 343 mL value. I obtained 0.03.
Use mols = grams/molar mass to determine mols UF6. I obtained 0.01.

Then U + ClFn ==> UF6 + xClF
.........0.03...0.01...0.03
You have 0.06 mols F in 0.01 mols UF6
(6 mols F/mol UF6) x (0.03/0.06) = 3 mols F/mol ClF; therefore, x = 3 and that makes the left side have 9 F. Put that together to obtain
U + 3ClF3 ==> UF6 + 3ClF