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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: EFox2413 on December 21, 2010, 11:37:25 AM

Title: Find empirical formula of compound X and Y
Post by: EFox2413 on December 21, 2010, 11:37:25 AM

I've worked through this problem but the back of the book has a different answer than the one I have.

The problem: A compound of X and Y is 1/3 X by mass. The atomic mass of element X is 1/3 the atomic mass of element Y. Find the empirical formula of the compound.

My work:
Xa / (Xa + Yb) = 1/3
X = 1/3Y

(1/3Y)a/((1/3Y)a + Yb) = 1/3
1/3Ya = 1/3 (1/3Ya + Yb)
1/3Ya = 1/9Ya + 1/3Yb
1/3a = 1/9a + 1/3b
2/9a = 1/3b
6/9a = b
2/3a = b

Therefore the empirical formula is X₃Y₂ because if a is 3 then b is 2.
but the answer in the book is X₂Y₃
Maybe I'm missing something obvious...? or book is wrong  ;D

Title: Re: Find empirical formula of compound X and Y
Post by: Hybrid on December 21, 2010, 12:09:21 PM

i solve it like u the smaller atomic weight element X  have the great contribution 3X and only 2Y??

Title: Re: Find empirical formula of compound X and Y
Post by: EFox2413 on December 21, 2010, 01:43:31 PM

Perhaps book is wrong then. It's the second edition so the answer in the back probably corresponds to a different problem that was in the first version but got changed slightly.

Title: Re: Find empirical formula of compound X and Y
Post by: Hybrid on December 21, 2010, 08:34:52 PM

tell me the name of the book or its link on google books

Title: Re: Find empirical formula of compound X and Y
Post by: EFox2413 on December 22, 2010, 03:45:43 PM

http://books.google.com/books?id=pucWPwAACAAJ&dq=chemistry+a+molecular+approach&hl=en&src=bmrr&ei=TGMSTaG7DYmqsAO3w5GaDw&sa=X&oi=book_result&ct=book-thumbnail&resnum=1&ved=0CDoQ6wEwAA