How many atoms of phosphorus are in 4.20 mol of copper (II) phosphate?

The formula for copper (II) phosphate is: Cu3 (PO4) 2

Thus, for every mol of Cu3 (PO4) 2, there is 2 mol of phosphate atoms.

2 x 4.40 = 8.80 mol.

Using Avagadro's number, we can now calculate the number of phosphate atoms:

N = n x N (A)

(N=number of atoms, n=amount in mole, N (A) = 6.02x10^23 - Avagadro's number)

Therefore:

N = 8.80 x (6.02x10^23)

= 5.29 x 10^24