[webassignbuddy]

I. The compound uranium hexafluoride, known as "hex" amongst nuclear engineering types can be prepared from elemental uranium (238 g/mol) and chlorine trifluoride via the reaction:

2 ClF₃(g) + U(s) UF₆(s) + Cl₂(g)

(1) Given that one begins with 15.90 L of ClF₃ (at 6.80 atm and 298 K) and 0.450 kg  of uranium metal, determine the number of equivalents of each reactant and indicate which species is the limiting reactant.

Eq (ClF₃): 2.21 (ANSWER KEY)
Eq (U): 1.89 (ANSWER KEY)
Limiting reactant: U (ANSWER KEY)

For this one this is what I did:

PV = nRT
PV/RT = n
(6.80 atm)(15.90 L)/(0.0821 L*atm/mol*K)(298 K) = n
108.12/24.5 = n
4.413 mol ClF₃= n (INCORRECT)
They divided this answer by 2! Why??

You can't do 4.413 mol ClF₃ x 1 mol ClF₃/2 mol ClF₃ = 2.2065. Can you??
From there, would I go about solving Eq U like this?
2.2065 mol ClF₃ x 1 mol U/2 mol ClF₃ = 1.10325.
But this is wrong too, since the answer is supposed to be 1.89.

(2) Assuming the same starting amounts as in part (1), what is the actual yield of UF₆(s) in kilograms if the percent yield of the process is only 74%?

[kriggy]

well:

n(U)=m/M = 0,45/0,238=1,89 mol
and because 1 mole of uranium reacts equivalent is:
eq= 1,89/1= 1,89

n(ClF₃) = PV/RT = 4,413 mol
so we have 4,413 moles of ClF₃ in mixture but because 2 moles react
eq= 4,413/2 = 2,205

They want to know how many equivalents of each reactant compared to the stoichiometry in equation.
Then, compare the number of equivalents to know which one is limiting reagent, and the lower amount is limiting reagent so its uranium.
And then, you can calculate the yield of UF₆ by using amount of uranium you have

[webassignbuddy]

well:

n(U)=m/M = 0,45/0,238=1,89 mol
and because 1 mole of uranium reacts equivalent is:
eq= 1,89/1= 1,89

n(ClF₃) = PV/RT = 4,413 mol
so we have 4,413 moles of ClF₃ in mixture but because 2 moles react
eq= 4,413/2 = 2,205

They want to know how many equivalents of each reactant compared to the stoichiometry in equation.
Then, compare the number of equivalents to know which one is limiting reagent, and the lower amount is limiting reagent so its uranium.
And then, you can calculate the yield of UF₆ by using amount of uranium you have

Oh ok, I got it!
Thanks!