how many iron atoms are contained in 354 grams of iron?

Molar mass Fe = 55.85g/mol
Mol Fe in 354g = 354/55.85 = 6.338 mol Fe
1 mol Fe = 6.022*10^23 atoms
6.338 mol Fe = 6.338*6.022*10^23 = 3.82 * 10^24 atoms.

…
conversion
354 g * mol / 55.8 g * 6022E23 atom/mol = 3.2E24 atoms

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