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Topic: Help finding value of x in compound  (Read 10770 times)

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molorov

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Help finding value of x in compound
« on: September 16, 2005, 10:55:01 PM »
This is the question that I'm trying to solve, can anyone help me out.

Elemental sulfur (1.256 g) is combined with fluorine, F2, to give a compound with the formula SFx, a very stable, colorless gas. If you have isolated 5.722 g of SFx, what is the value of x?

Karakth

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Re:Help finding value of x in compound
« Reply #1 on: September 17, 2005, 05:55:22 AM »
What have you done so far? Have you attempted the question?

Quote
If asking a question here at the forums, you MUST show that you have at least attempted the problem. We are here to help, not do your homework for you. Any questions posted without showing that you have attempted to answer the question yourself will be deleted. Thank you. ~jdurg

Anyway, as in all chemistry questions, never compare using masses. Use moles.

HDC

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Re:Help finding value of x in compound
« Reply #2 on: September 18, 2005, 01:17:11 PM »
Molorov,

I may have a possible solution to your problem since it kind of resembles several, similar, problems I'm having problems with.

First thing I did was to state the chemical equation.  (It may or may not help.)
S8(s) + F2(g) --> SFx(g)

Then I stated the masses of the given compounds:

mass SFx = 5.722g SFx
mass S = 1.256g S

Then I calculated the mass percentages of S and F in the compound:
%S in SFx = (1.256g / 5.722g) * 100% = 21.95%
%F in SFx = 100% - 21.95% = 78.05%

Next I converted those percentages to moles:
mol S = 21.95g S * (1 mol S / 32.07g S) = .6844 mol S
mol F = 78.05g F * (1 mol F / 19.00g F) = 4.108 mol F

Next I find the simplest whole number mole ratios between S and F by
by dividing both moles by smallest mole of the two:
S = .6844 / .6844 = 1
F = 4.108 / .6844 = 6

Finally I find the empirical formula for SFx: S1F6

Don't know if its right or not, but that's how I would do it.  

HDC

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Re:Help finding value of x in compound
« Reply #3 on: September 18, 2005, 03:11:38 PM »
Then I calculated the mass percentages of S and F in the compound:
%S in SFx = (1.256g / 5.722g) * 100% = 21.95%
%F in SFx = 100% - 21.95% = 78.05%

Next I converted those percentages to moles:
mol S = 21.95g S * (1 mol S / 32.07g S) = .6844 mol S
mol F = 78.05g F * (1 mol F / 19.00g F) = 4.108 mol F

You are reaching left ear with right hand.

5.722g SFx contains 1.256g S and 5.722-1.256=4.466g F
Convert these mases to moles. You don't need to go through percentages.

But apart from the fact that you have took unnecesarilly long trip, you have reached correct result ;)

Please read Karakth's post!
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