Question

For a particular redox reaction ClO2– is oxidized to ClO4– and Fe3 is reduced to Fe2 . Complete and balance the equation for this reaction in basic solution. Phases are optional.
Please HELP, I don't know how to balance redox reactions in basic solutions...!

Answer 1

We have to balance the equation in basic medium:
ClO₂⁻ → ClO₄⁻
Chlorine atoms are balanced 
we will balance oxygen atoms by adding water to the side with less oxygen
2 H₂O + ClO₂⁻ → ClO₄⁻
Now balance hydrogens by adding H⁺ first
2 H₂O + ClO₂⁻ → 4 H⁺ + ClO₄⁻
The charge will be balanced by adding electrons to side where positive charge is more
2 H₂O + ClO₂⁻ →  4 e + 4 H⁺ + ClO₄⁻
Now balance H⁺ by adding same number of OH⁻ in both sides
2 H₂O + ClO₂⁻ + 4OH⁻ →  4 e + 4 H⁺ + 4OH⁻ + ClO₄⁻
H⁺ will neutralize OH⁻ to give water
2 H₂O + ClO₂⁻ + 4 OH⁻ → 4 e + 4 H₂O + ClO₄⁻
Balanced half reaction will be:
ClO₂⁻ + 4 OH⁻ → 4 e + 2 H₂O + ClO₄⁻ → (1)
Now balance the second half (reduction):
Fe⁺³ → Fe⁺²
Balance charge by adding electrons:
e + Fe⁺³ → Fe⁺² → (2) Multiply by 4 and add the two equations to get:
ClO₂⁻ + 4 OH⁻ + 4 Fe⁺³  → 4 Fe⁺² + 2 H₂O + ClO₄⁻