Iron(III) oxide is formed when iron combines with oxygen in the air. How many grams of Fe203 are formed when 6.7 g of Fe reacts completely with oxygen?
Fe + 02 --> Fe203 (unbalanced equation)

Mass = 9.58 g  

Explanation:

Given data:

Mass of Fe₂O₃ formed = ?

Mass of Fe = 6.7 g

Solution:

Chemical equation:

4Fe + 3O₂        →    2Fe₂O₃

Number of moles of Fe:

Number of moles = mass/molar mass

Number of moles = 6.7 g/ 55.8 g/mol

Number of moles = 0.12 mol

now we will compare the moles of Fe and Fe₂O₃.

                         Fe         :          Fe₂O₃

                           4         :              2

                         0.12       :          2/4×0.12 = 0.06 mol

Mass of Fe₂O₃:

Mass = number of moles × molar mass

Mass = 0.06 mol  × 159.69 g/mol

Mass = 9.58 g  

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