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Topic: on finding empirical & molecular forumulas  (Read 5374 times)

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Offline yeliel87

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on finding empirical & molecular forumulas
« on: April 29, 2010, 08:12:35 PM »
I've been working on this problem for the past hour but I can't seem to get the right answer, please help me figure it out!
A compound containing only C, H & O was extracted from the bark of the sassafras tree. The combustion of 80.7 mg produced 219 mg of CO2 and 44.9 mg of H2O. The molar mass of the compound was 162 g/mol. Determine the empirical & molecular formulas.

Here's what I've done:
I converted 219 mg to 0.219 g and figured out that there are 0.004976 mol of C
I did the same with H and found 0.00052724 mol H
I multiplied 0.004976 mol of C * 12.0107 g/mol to get 0.059765 g C
I multiplied 0.00052724 mol H * 1.0079 g/mol to get 0.000531426 g H
I added 0.059765 g C + 0.000531426 g H together and subtracted them from 0.0807 g to get 0.020403 g O
I converted 0.020403 g O to mols and got 0.00127 mol O
I divided all 3 by the smallest # (0.00052724 mol H) which game me something like 1 mol H, 2.4 mol O and 9.43 mol C which doesn't seem right. What am I doing wrong?


Offline yeliel87

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Re: on finding empirical & molecular forumulas
« Reply #1 on: April 29, 2010, 09:53:01 PM »
Never mind, I got it.

Offline Borek

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Re: on finding empirical & molecular forumulas
« Reply #2 on: April 30, 2010, 03:11:43 AM »
I did the same with H and found 0.00052724 mol H

I guess that's where your calculations went astray.
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