Question

What is the molar ratio for the following equation after it has been properly balanced?

Answer 1

6 Na + 1 Fe₂O₃ → 3 Na₂O + 6 Fe

Explanation

Method One: Refer to electron transfers.

Oxidation states:

• Na: from 0 to +1; loses one electron.
• Fe: from +3 to 0; gains three electrons.

Each mole of Fe₂O₃ contains two Fe atoms and will gain 2 × 3 = 6 electrons during the reaction. It takes 6 moles of Na to supply all those electrons.

6 Na + 1 Fe₂O₃ → ? Na₂O + ? Fe

• There are two moles of Na atoms in each mole of Na₂O. 6 moles of Na will make 3 moles of Na₂O.
• There are two moles of Fe atoms in each mole of Fe₂O₃. 1 mole of Fe₂O₃ will make 2 moles of Fe.

6 Na + 1 Fe₂O₃ → 3 Na₂O + 2 Fe

Method Two: Atoms conserve.

Fe₂O₃ has the largest number of atoms among one mole of all four species in this reaction. Assume one as its coefficient.

? Na + 1 Fe₂O₃ → ? Na₂O + ? Fe

There are two moles of Fe atoms and three moles of O atoms in each mol of Fe₂O₃. One mole of Fe₂O₃ contains two moles of Fe and three moles of O. There are one mole of O atom in every mole of Na₂O. Three moles of O will go to three moles of Na₂O.

? Na + 1 Fe₂O₃ → 3 Na₂O + 2 Fe

Each mole of Na₂O contains two moles of Na. Three moles of Na₂O will contain six moles of Na.

6 Na + 1 Fe₂O₃ → 3 Na₂O + 2 Fe

Simplify the coefficients. All coefficients in this equation are now full number and relatively prime. Hence the equation is balanced.

6 Na + 1 Fe₂O₃ → 3 Na₂O + 2 Fe