Balancing Half-Reactions: Determining H2O2 Concentration with KMnO4 Titration

[DumbDuck]

Problem:
Determine concentration of H2O2 with Titration of KMnO4

Balance the equation and create a net ionic equation then balance using redox techniques and replace spectator ions

Balanced Equation:
5H2O2 + 2KMnO4 + H2SO4 ==> K2SO4 + MnSO4 + H2O + O2

My Work:
I eliminated all spectators and my net ionic equation was

16H(+) + 18O(2-) ==> 8H20 + 5O2

This cannot be correct, since putting this into a half-reaction

8H2O + 16H(+) ==> 8H2O + 16H(+) there is no need for e- and therefore is not a redox reaction. If I have the correct ionic equation I'm sure I can figure out the rest

 

[chemisttree]

Problem:
Determine concentration of H2O2 with Titration of KMnO4

Balance the equation and create a net ionic equation then balance using redox techniques and replace spectator ions

Balanced Equation:
5H2O2 + 2KMnO4 + H2SO4 ==> K2SO4 + MnSO4 + H2O + O2

My Work:
I eliminated all spectators and my net ionic equation was

16H(+) + 18O(2-) ==> 8H20 + 5O2

This cannot be correct, since putting this into a half-reaction

8H2O + 16H(+) ==> 8H2O + 16H(+) there is no need for e- and therefore is not a redox reaction. If I have the correct ionic equation I'm sure I can figure out the rest

Half reactions are reactions where the oxidant's reaction is shown separately from the reductant's reaction. It can be generalized as:

[O] + e- ----> [O]- ( or [O]+ + e- ------> [O] )

and

[R] -------> [R]+ + e- ( or [R]- ------> [R] + e- )

where [O] is the oxidant and [R] is the reductant.

In your example what is the reductant and the oxidant? Hint: H+ is neither...

 

[Blueshift5]

Thank you for sharing your work. Your balanced equation and net ionic equation are correct. However, in order to use redox techniques and determine the concentration of H2O2, you will need to set up the half-reactions for both the oxidation and reduction reactions. In this case, the reduction half-reaction would be 2MnO4- + 16H+ + 10e- --> 2Mn2+ + 8H2O and the oxidation half-reaction would be 5H2O2 --> 5O2 + 10H+ + 10e-. By balancing the number of electrons in each half-reaction, you can then set them equal to each other and solve for the concentration of H2O2. I hope this helps in solving the problem.