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Topic: Empirical formulas laboratory problem  (Read 6093 times)

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Offline CValley

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Empirical formulas laboratory problem
« on: March 28, 2010, 04:14:23 PM »
Here is the original questions(s).

A sample of pure copper is covered with an excess of powdered elemental sulfur. The following data were collected.

Mass of crucible and lid: 19.914g
Mass of copper, crucible, and lid: 21.697g

The mixture was heated to a temperature where a reaction occurred and the excess sulfur was volatized. Upon cooling the following data was recorded.

Mass of compound, crucible, and lid: 23.044

Complete the following data analysis
Mass of sulfur in compound.
Moles of sulfur in compound.
Mass of copper in compound.
Moles of copper in compound.
Empirical formula of the compound.

I think I'm messing up somewhere because when I check the mole ratio of the two elements I'm not getting a whole number. Any help would be appreciated greatly.

Online Borek

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Re: Empirical formulas laboratory problem
« Reply #1 on: March 28, 2010, 04:22:41 PM »
You would never get exactly whole number, you should get something close to one. That's what experimental errors are about.
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Offline CValley

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Re: Empirical formulas laboratory problem
« Reply #2 on: March 28, 2010, 05:16:36 PM »
Here's what I've done.

23.044-21.697= 1.347 g sulfur
21.697-19.914= 1.783 g copper
1.347/32.065=.0420 moles of sulfur
1.783/63.546=.0281 moles of copper
.0420/.0281=1.495? I thought that if everything was done right then this number would be a bit closer to a whole number, but I can't figure out what I've done wrong.

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Re: Empirical formulas laboratory problem
« Reply #3 on: March 28, 2010, 05:40:21 PM »
Are you sure what was left in the crucible was a metallic copper?
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Offline CValley

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Re: Empirical formulas laboratory problem
« Reply #4 on: March 28, 2010, 05:49:33 PM »
The question says it is pure copper covered with an excess of powdered elemental sulfur. Sorry about the mistake.

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