Calculate the number of iron atoms in a sample of iron(III) oxide . Be sure your answer has a unit symbol if necessary, and round it to significant digits.

Explanation:

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In this case, since the mass of iron (III) oxide is missing we use 80.0 g as found on similar problems. In such a way, since iron (III) molar mass is 159.70 g/mol, one mole of iron (III) oxide has two moles of iron (subscript) and one mole of atoms of iron have 6.022x10²³ atoms (Avogadro's number), the correct number of atoms in such sample is:

Which is shown with three significant figures as 80.0 g has three as well.

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