Finding mass of 1 atom given molar mass & density?

Question

Finding mass of 1 atom given molar mass & density?

I) Given the density of something (e.g. platinum, aluminum) and the molar masses, how do you figure out the mass of an atom of each?

2) Then how do you find out how many atoms are in a meter^3

Answer 1

1. Take aluminum (Al) for example. Al has a relative molar mass of 27 (approx). So if you get 27 g of Al you have 1 mol of Al atoms. But 1 mol contains 6.02x10^23 atoms. So the mass of an atom equals:

m = 27 / 6.02x10^23, m = 4.5x10^(-23) g

2. 1 m^3 is 10^6 cm^3. The density of Al is 2.7 g/cm^3, so the mass of 1 m^3 Al is:

m = d x V = 2.7x10^6 g

Find the moles of Al:

n = m/Ar = 2.7x10^6/27 = 10^5 mol

Then find the atoms N of Al:

N = n * 6.02x10^23 = 10^5 * 6.02x10^23 = 6.02x10^28

Answer 2

1) look at a peroidic table!! it shows molar masses, and from there, search online for a "mole map" it will give formulae for converting those things.

2) i dunno i took chem last year