Final answer:
The coefficient of OH⁻ is 6 when the redox equation is balanced using the set of smallest whole numbers.
Step-by-step explanation:
The balanced redox equation is:
2 Fe + 3 Cl2 + 6 OH- → 2 Fe(OH)3 + 6 Cl-
In the balanced equation, the coefficient of OH- is 6.
To balance the equation, we start by determining the oxidation numbers of the species involved. The Fe atoms go from an oxidation state of 0 on the left side to +3 on the right side, while the Cl atoms go from 0 to -1. This means that Fe is being oxidized and Cl is being reduced.
Next, we balance the atoms other than hydrogen and oxygen, which are already balanced in this equation. Since there are 2 Fe atoms on the left side, we need 2 Fe(OH)3 on the right side. To balance the chlorine atoms, we need 6 Cl- on the left side. Finally, to balance the charge, we add 6 OH- on the left side.