A 7.50-g sample of iron is heated in oxygen to form an iron oxide. if 10.71 g of the oxide is formed, what is its empirical formula

Answer is: empirical formula is Fe₂O₃.

m (Fe) = 7,50 g.

m (iron oxide) = 10,71 g.

n (Fe) = m (Fe) : M (Fe).

n (Fe) = 7,50 g : 55,85 g/mol = 0,134 mol.

m (O) = m (iron oxide) - m (Fe).

m (O) = 10,71 g - 7,50 g = 3,21 g.

n (O) = 3,21 g : 16 g/mol = 0,20 mol.

n (Fe) : n (O) = 0,134 mol : 0,2 mol = 2 : 3.