Question

An iron compound is 27.925% iron by mass. Find the number of atoms of Fe present in 5 g of the compound. (Molar mass of Fe=55.85g/mol)

Answer 1

Mass % of Fe in the compound = 27.925 %

Therefore, 100 g of Compound contains 27.925 g of Fe.

So, 5 g of compound will contain (27.925 x 5) / 100 = 1.3962 g.

55.85 g of Fe contains 6.023 x 10²³ atoms of Fe.

Therefore, 1.3962 g of Fe will contain (6.023 x 10²³ x 1.3962) / 55.85 = 1.505 x 10²² atoms of Fe.