How would you balance the following equation: Fe+O2 --> Fe2O3?

1 Answer
Nov 2, 2015

4Fe + 3O_2 rarr 2Fe_2O_3

Explanation:

Step 1: Tally the number of atoms based on subscript.

Fe + O_2 rarr Fe_2O_3 (unbalanced)

left side: Fe = 1; O = 2
right side: Fe = 2; O = 3

Step 2: Start balancing the simple molecules first, in this case the O_2

Fe + color (green) 3O_2 rarr Fe_2O_3

left side: Fe = 1; O = 2 x color (green) 3 = 6
right side: Fe = 2; O = 3

Since there are now 6 O atoms on the left, there must also be 6 O atoms on the right. Notice that the right hand is one big molecule so whatever coefficient you would use to balance the O atoms, you would also need to apply to the bonded Fe atom.

Fe + 3O_2 rarr color (red) 2Fe_2O_3

left side: Fe = 1; O = 2 x 3 = 6
right side: Fe = 2 x color (red) 2 = 4; O = 3 x color (red) 2 = 6

Step 3: Now balance the rest of the equation.

color (blue) 4Fe + 3O_2 rarr 2Fe_2O_3

left side: Fe = 1 x color (blue) 4 = 4; O = 2 x 3 = 6
right side: Fe = 2 x 2 = 4; O = 3 x 2 = 6

The equation is now balanced.