Question

For a particular redox reaction, SO₃^2- is oxidized to SO₄^2- and Fe³⁺ is reduced to Fe²⁺. Complete and balance the equation for this reaction in basic solution. The phases are optional. 

balanced reaction: _______ 

Answer 1

Answer 2

Answer 3

The balancing of the equation is shown below.

Write both half cell reactions.

First half-reaction,

Fe3+ ---------Fe2+

Balance electrons on both sides

Fe3+ + 1e- ---------Fe2+

Write the other half-reaction

SO3^2- --------SO4^2-

Balance O by adding H2O to the other side

SO3^2- + H2O ----------SO4^2-

Add H+ to balance Hydrogen on the other side

SO3^2- + H2O ----------SO4^2- + 2H+

Now for primary reaction add OH- ion on both sides equivalent to the number of H+ added

SO3^2- + H2O + 2OH- ----------SO4^2- + 2H+ + 2OH-

Add H+ and OH- to form H2O

SO3^2- + H2O + 2OH- ----------SO4^2- + 2H2O

Balance charges and cancel common terms

SO3^2- + 2OH- ----------SO4^2- + H2O + 2e-

Multiply the first half reaction with 2 (2e- involved in the overall reaction)

2Fe3+ + 2e- ------------- 2Fe2+

Add both half cell reactions

2Fe3+ + 2e- + SO3^2- + 2OH- -------------> 2Fe2+ + SO4^2- + H2O + 2e-

Cancel common terms gives us the balalnced redox reaction.

2Fe3+ + SO3^2- + 2OH- -------------> 2Fe2+ + SO4^2- + H2O