1. Determine the ratio of oxygen atoms to sulfur atoms in CuSO4:

* The formula CuSO4 indicates that there are 4 oxygen atoms for every 1 sulfur atom.

2. Calculate the number of sulfur atoms:

* Since we have 3.50 x 10^23 oxygen atoms, we can find the number of sulfur atoms by dividing by the ratio:

(3.50 x 10^23 oxygen atoms) / (4 oxygen atoms/sulfur atom) = 8.75 x 10^22 sulfur atoms

3. Convert sulfur atoms to moles:

* Use Avogadro's number (6.022 x 10^23 atoms/mole) to convert sulfur atoms to moles:

(8.75 x 10^22 sulfur atoms) / (6.022 x 10^23 atoms/mole) = 0.145 moles of sulfur

Therefore, the sample of CuSO4 contains 0.145 moles of sulfur.