Calculating number of atoms in an alloy

[digeratus]

Homework Statement

Germanium forms a substitutional solid solution with silicon. Compute the number of germanium atoms per cubic centimeter for a germanium-silicon alloy that contains 15 wt% Ge and 85 wt% Si. The densities of pure germanium and silicon are 5.32 and 2.33 g/cm3, respectively.

Homework Equations

I'm not sure on these. I will put the ones I think are applicable.

C'1=(C1 A2)/((C1 A2)+(C2 A1))

p (avg) = ((C'1 A1)+(C'2 A2))/((C'1 A1/p1)+(C'2 A2/p2))

C = weight percent = wt%
C' = atomic percent
p = density
A = atomic weight

The Attempt at a Solution

I can put the numbers into get the atomic percents and the density of the alloy. I calculated 6.389 atomic% Ge and 93.611 atomic% Si. For the density of the alloy, I got 2.5445 g/cm3. The only problem is that I don't know how to get the number of Ge atoms in one cubic centimeter. How do I get there from where I am?

 

[superconduct]

No. of atoms of Ge
=(2.5445/72.64)(6.02x10^23)= 2.11x10^22