Confusing chemistry question

Question

Water is added to 4.267g of UF6. the only products are 3.730g of a solid containg only uranium, oxygen, and fluorine and .970g of a gas. The gas is 95.0% fluorine and the remainder is hydrogen.

1. What fraction of the fluorine of the orginal is in the solid and what fraction in the gas after the reaction?

2.What is the formula of the solid product?

Answer 1

UF6 & H2O --> HF & ......

find moles, using molar masses:

4.267 g  @ 352.0 g/mol  0.0121 moles of UF6, which has  six times as many moles of fluoride = 0.0727 mol Fluoride

0.970  @ 20.0 g/mol = 0.0485 moles of fluoride left the UF6 as HF

0.0485 mol F / 0.0727 mol F = 2/3rds of the Fluoride was released from the UF6

your first answer is 1/3 of the fluoride is still in the original compound,

& 2/3 of the original fluoride is now in the gas after the reaction

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UF6 & 2H2O --> UO2F2  & 4HF

your answer is: UO2F2 is your new solid

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as a check on our work we will see if 3.730g of UO2F2 is the amount that should be produced from 4.267 grams of UF6, using the molar mass of each compound:

4.267 g UF6 @ 308 g/mol UO2F2 / 352 g/mol UF6 = 3.73g UO2F2 should be & was produced

it checks out

Answer 2

It's worded a bit strange; let's see if we can get through it.

Uranium = 238 g/mol; Florine=19 g/mol ;Oxygen=16 g/mol

In 1 mol of UF6, 114g of florine present.

# moles UF6 in 4.267g = 4.267g / 352g/mol = 0.01212 mol

g of F in UF6: 4.267g of UF6 = (0.01212mol) (114 g/mol) = 1.3819g

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(The 114 comes from the fact that 6 F are in UF6. 19*6 = 114)

In the gas, 95% of 0.97g is florine. Mass of florine in gas then is, (0.95)(0.97) = 0.9215 g

Mass of florine in solid = Mass total - mass that's in gaseous form: 1.3819g - 0.9215g = 0.4604g

Therefore, % of florine in solid = (0.4604 g/ 1.3819g)*100% = 33.32%

and % of florine in gas = 100% - 33.32% = 66.68%  

So, approximately 1/2 and 2/3 or 33.33% and 66.66 %<~~Answer

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2.) Mass of H2O reacted = (3.730g +0.97g) - 4.267g = 0.433g

Mass of O2 in solid = ( 0.433g / 18g )(16g) = 0.3849g

Therefore, mass of uranium in solid form = 3.730g - ( 0.3849g + 0.4604g ) = 2.8847g

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So we have U: 2.8847g / 238 g/mol = 0.012 mol

F: 0.4604 g/ 19 g/mol = 0.024 mol

O: 0.34849/16 g/mol = 0.024 mol

If you can't see the 2:1:1 ratio, simply divide by the smallest number:

0.012/0.012 = 1 (U)

0.024/0.012 = 2(F)

0.024/0.012 = 2(O)

Therefore, the formula of the unknown is UF2O2

and the overall reaction:

UF6 + 2H2O --> UF2O2 + 4HF