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Topic: Empirical Problem  (Read 10864 times)

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Offline JonathanEyoon

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Empirical Problem
« on: February 16, 2008, 03:30:33 PM »
A compound was found to contain 90.6% lead (Pb) and 9.4% oxygen. The empirical formula for this compound is



I'm so lost =/ Help
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Offline Borek

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Re: Empirical Problem
« Reply #1 on: February 16, 2008, 03:37:57 PM »
How many moles of lead in 100g of the compound? How many moles of oxygen? What is their ratio?
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Offline JonathanEyoon

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Re: Empirical Problem
« Reply #2 on: February 16, 2008, 03:42:01 PM »
 ???
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Offline Arkcon

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Re: Empirical Problem
« Reply #3 on: February 16, 2008, 04:17:35 PM »
OK, try to visualize, the compound is 90.6% lead and 9.4 % oxygen, by weight.  You know that compounds aren't given in percents -- there is no compound PB90.6O9.4, right?  What number is supposed to go in the subscripts, and how do you get it. 

Hint: What "weighs" more, a beaker full of lead or a beaker full of oxygen, and where can you find those numbers published?
« Last Edit: February 17, 2008, 11:29:43 AM by Arkcon »
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Offline JonathanEyoon

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Re: Empirical Problem
« Reply #4 on: February 16, 2008, 05:09:17 PM »
ok let me see if I got this right.  so we assume we have a 100 grams of the two elements and then divide by their respective atomic number?
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Offline Borek

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Re: Empirical Problem
« Reply #5 on: February 16, 2008, 05:13:05 PM »
Assuming you have 100g of compound and it contains 90.6% of lead - what is mass of lead in this sample?
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Offline JonathanEyoon

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Re: Empirical Problem
« Reply #6 on: February 16, 2008, 05:20:28 PM »
Quote from: Borek on February 16, 2008, 05:13:05 PM
Assuming you have 100g of compound and it contains 90.6% of lead - what is mass of lead in this sample?


it's going to be 90.6 / 207.2?
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Offline JonathanEyoon

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Re: Empirical Problem
« Reply #7 on: February 16, 2008, 05:39:41 PM »
ok I think i go it.


Is it Pb3O4?
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Offline Borek

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Re: Empirical Problem
« Reply #8 on: February 16, 2008, 05:44:41 PM »
Quote from: JonathanEyoon on February 16, 2008, 05:20:28 PM
Quote from: Borek on February 16, 2008, 05:13:05 PM
Assuming you have 100g of compound and it contains 90.6% of lead - what is mass of lead in this sample?
it's going to be 90.6 / 207.2?

This is next step - number of moles of lead. I was asking for 90.6 grams.

Quote from: JonathanEyoon on February 16, 2008, 05:39:41 PM
Is it Pb3O4?

Yes :)
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Offline JonathanEyoon

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Re: Empirical Problem
« Reply #9 on: February 16, 2008, 05:50:18 PM »
yay  :)
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