# Quick moles problem

1. Jul 10, 2009

### Attraction

1. The problem statement, all variables and given/known data

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

3. 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.

2. Jul 10, 2009

### symbolipoint

Simple unit conversion and seeing the ratio of items. You need to know the meaning of a mole.

3. Jul 10, 2009

### Attraction

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.

Last edited: Jul 10, 2009
4. Jul 10, 2009

### Staff: Mentor

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

How many atoms per mole?

5. Jul 10, 2009

### Attraction

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. Jul 10, 2009

### Staff: Mentor

Yes.

7. Jul 10, 2009

### Attraction

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. Jul 11, 2009

### symbolipoint

Finally, Yes.