Quick moles problem

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Homework Statement



If you have 4.5 x 1020 molecules of SnO2, how many moles of O do you have?


The Attempt at a Solution



I'm really getting the hang of moles lately but what is bothering me in this question is 4.5 x 1020 molecules of SnO2.

If it was one molecule, you would have 2 moles of O yes?
Therefore in 4.5 x 1020 molecules, you have 4.5 x 1020 multiplied by 2? But that doesn't give me the correct answer.
 

Answers and Replies

  • #2
symbolipoint
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Simple unit conversion and seeing the ratio of items. You need to know the meaning of a mole.
 
  • #3
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Simple unit conversion and seeing the ratio of items. You need to know the meaning of a mole.

Would I be right in saying that there would be 2 mols of O in ONE molecule of SnO2? I think so. So that would be 2 x Avogadros #.

Therefore in 4.5 x 1020 molecules of SnO2, there should be 2 mols of O x 4.5 x 1020 molecules? I know thats not right though. Where am I going wrong.
 
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  • #4
Borek
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Would I be right in saying that there would be 2 mols of O in ONE molecule of SnO2?

No. There will be two ATOMS of oxygen in one molecule on SnO2.

How many atoms per mole?
 
  • #5
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No. There will be two ATOMS of oxygen in one molecule on SnO2.

How many atoms per mole?

6.022x1023 per mole yes?, my problem is figuring out how many mols of O are in 1 molecule of SnO2.

So I must be wrong there with Avogadros number then?
 
  • #6
Borek
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Yes.
 
  • #7
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I figured it out. Pretty easy. There is 2 atoms of O in the molecule. Therefore there is 2 x 4.5 x 1020 atoms in 4.5 x 1020 molecules... simple.

Then convert atoms into moles by dividing by avogadros #.

thanks.
 
  • #8
symbolipoint
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Finally, Yes.
 

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