To calculate the number of moles in 5.0 x 10^25 atoms of iron, we can use Avogadro's number, which is approximately 6.022 x 10^23 atoms per mole. Avogadro's number represents the number of atoms or molecules present in one mole of a substance.

We can set up a proportion to find the number of moles:

(Number of moles of iron) / (Number of atoms of iron) = (1 mole) / (6.022 x 10^23 atoms)

Substituting the given number of atoms (5.0 x 10^25 atoms) into the equation:

(Number of moles of iron) / (5.0 x 10^25 atoms) = (1 mole) / (6.022 x 10^23 atoms)

Solving for the number of moles of iron:

(Number of moles of iron) = (5.0 x 10^25 atoms) * (1 mole / 6.022 x 10^23 atoms)

(Number of moles of iron) ≈ 8.30 moles

Therefore, there are approximately 8.30 moles in 5.0 x 10^25 atoms of iron.