Question

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

Answer 1

`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.