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Question regarding empirical formula and molecular formula(finding 2 variables)A Lvel

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mutineer123
#1
Mar5-12, 07:56 PM
P: 93
1. The problem statement, all variables and given/known data

http://www.xtremepapers.com/CIE/Inte..._s11_qp_12.pdf

question 10




2. Relevant equations




3. The attempt at a solution
The way I am doing it, is to get two equations in terms of x and y and then equate them. For the first equation I used the fact that all of the element's individual atomic masses will add up to 571.5. So i got 27x + 28.1y = 172
My problem now is how to get the second equation? I think it has something to do with the empirical formula, but I can't figure it out. Help!
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sjb-2812
#2
Mar6-12, 07:20 AM
P: 427
If you remove the Al and Si from the formula, what is the charge on the resulting ion?
Borek
#3
Mar6-12, 07:34 AM
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What is 14.04% of 571.5?

mutineer123
#4
Mar6-12, 10:43 PM
P: 93
Question regarding empirical formula and molecular formula(finding 2 variables)A Lvel

Quote Quote by Borek View Post
What is 14.04% of 571.5?
I think I got it, thanks to you. So for x we find 14.17% of 571.5. That answer we divide by 27, (because we know that the mole of aluminium is 1), and the x i got is 2.999(pretty close to one of the options). Same for y. Thanks!


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