Here is a very good site for redox. It gives the rules for determining oxidation states as well as rules for balancing redox equations plus many other aspects of redox reactions.
https://www.chemteam.info/Redox/Redox.html
MnO4- + H2SO3 --> SO42- + Mn2+
If you will study that sites rules for determining oxidation states as I apply them to this problem you will see how it's done.
The elements changing oxidation states are Mn and S. For Mn, you know O is -2.Then 4*-2 = -8. There is a -1 charge on the ion so Mn must be +7. On the other side Mn^2+ is +2. So the change is +7 to +2 or 5 electrons gained. For S in H2SO3, H is 2*+1 = 2. O is 3*-2 = -6. So for H2SO3 to be neutral, S must be +4. On the right, S in SO4^2- is +6. You should verify that. S goes from +4 to +6 for a loss of 2 electrons. Electron loss in redox equations always must be equal to electrons gained. Mn is change of 5, S is change of 2 so you multiply Mn by 2 to get 10 electrons changed. Multiply S by 5 to get 10 electrons changed. The answer to the question of how many electrons are transferred is 10. Hope this helps.
When the following equation is balanced in an acidic solution how many electrons are transferred?
MnO4- + H2SO3 --> SO42- + Mn2+
1 answer
4 answers