[Solved] How to find number of atoms in a sample of an element

[Homey]

Hello,

 

How would I go about finding the number of atoms in an element sample, given the density.

 

I have found the volume and mass of my sample and presume I should work it like such:

 

[Number of atoms] = [Avogadro's Number] * (density) * volume/(atomic weight)

 

In my case, I have aluminum foil of 27g, 27g/mol, and 10 cm³

When using the equation above I end up with six atoms?

 

I suppose the error is in the equation(but I don't know)

 

Thanks

Edited June 22, 2017 by Homey

[DrP]

Haven't done this for ages... but just a quick question... If it is 27g/mol and you have 27 grams of aluminium, then wouldn't that mean that you have 1 mol of aluminium and thus Avagadro's number of atoms?

[swansont]

When using the equation above I end up with six atoms?

 

 

What is Avogadro's number?

[Homey]

Haven't done this for ages... but just a quick question... If it is 27g/mol and you have 27 grams of aluminium, then wouldn't that mean that you have 1 mol of aluminium and thus Avagadro's number of atoms?

 

 

Yes that is what I got but I was a bit skeptical of it but thanks for the clarification

[DrP]

ah... thus the 6 atoms... I think it is about 6 x 10^24 or something like that. ;-) (Just looked it up - it's x10^23 - still huge though)

[OldChemE]

Look at the units associated with Avogadro's number, and you should be able to write a much simpler equation that directly converts grams to atoms.

 

When you have a problem involving different units of measure, you can use the units to determine the appropriate equation.

 

Avogadro's number is atoms/mole, atomic weight is grams/mole, sample size is grams. How could you multiply or divide these three sets of units in order to have a result which is in units of atoms? Do this and you will have your answer.

[Homey]

Look at the units associated with Avogadro's number, and you should be able to write a much simpler equation that directly converts grams to atoms.

 

When you have a problem involving different units of measure, you can use the units to determine the appropriate equation.

 

Avogadro's number is atoms/mole, atomic weight is grams/mole, sample size is grams. How could you multiply or divide these three sets of units in order to have a result which is in units of atoms? Do this and you will have your answer.

 

Thanks, this seemed to be the most straightforward away about working my problem