[iAre Teh Lejend]

How do I know what to include and what not to include in half equations ?

For example;

(MnO4)^- + (Fe)^2+ + H^+ --> Mn^2+ + Fe^3+ + H2O

Why is the half equation for the reduction;

(MnO4)- + 5e --> Mn^2+

and not;

Mn^+7 + 5e- --> Mn^2+

Someone please explain the concept to me of half equations in detail please.

[EierVonSatan]

That's not the half-equation for that reaction...it's not balanced. Half-equations need to be balanced in terms of particles and in terms of charge.

It's not Mn⁷⁺ + 5e^- ---> Mn²⁺ as Mn⁷⁺ as a species, does not exist in the full equation.

The two half-equations are

MnO₄^- + 8H⁺ + 5e^- ---> Mn²⁺ + 4H₂O
Fe²⁺ ---> Fe³⁺ + e^-

Does that make sense?

[dmccririck]

(Original post by iAre Teh Lejend)
How do I know what to include and what not to include in half equations ?

For example;

(MnO4)^- + (Fe)^2+ + H^+ --> Mn^2+ + Fe^3+ + H2O

Why is the half equation for the reduction;

(MnO4)- + 5e --> Mn^2+

and not;

Mn^+7 + 5e- --> Mn^2+

Someone please explain the concept to me of half equations in detail please.

You've confused me now! Your top two equations aren't balanced for oxygen or charge...

[iAre Teh Lejend]

(Original post by dmccririck)
You've confused me now! Your top two equations aren't balanced for oxygen or charge...

Sorry bro, I meant to add the water and H+ ions where needed, but my question is about Mn so i forgot to add those.