Where are the most atoms located: in 4.60 g of iron oxide (3) or in 4.00 g of iron oxide (2)?

Solution
1. The formula of iron oxide (3) is Fe2O3, and the formula of iron oxide (2) is FeO. Let’s find their molecular weights:
Iron oxide (3): 56 * 2 + 16 * 3 = 160 g / mol;
Iron oxide (2): 56 + 16 = 72 g / mol;
2. Find the amount of substance in iron oxide (3):
4.6 / 160 = 0.029 mol;
3. Find the amount of substance in iron oxide (2):
4/72 = 0.056 mol;
4. Find the number of atoms in iron oxide (3):
0.029 * 6.02 * 10 ^ 23 = 1.75 * 10 ^ 22 atoms;
5. Find the number of atoms in iron oxide (2):
0.056 * 6.02 * 10 ^ 23 = 3.37 * 10 ^ 22 atoms;
Answer: more atoms are found in iron oxide (2).