Question time! It's been a while.
How do we know whether iron has been reduced or oxidised in a redox reaction if the question does not explicitly state so?
For e.g. Potassium manganate (VII) + Iron (II) ethanedioate
I don't think iron is oxidised in this case.
Oh yeah, it applies to other cations with variable oxidation states too (copper, zinc, ... those oh-so-unstable-cations)
Thanks for the clarification.
Originally posted by Garrick_3658:Question time! It's been a while.
How do we know whether iron has been reduced or oxidised in a redox reaction if the question does not explicitly state so?
For e.g. Potassium manganate (VII) + Iron (II) ethanedioateI don't think iron is oxidised in this case.
Oh yeah, it applies to other cations with variable oxidation states too (copper, zinc, ... those oh-so-unstable-cations)
Thanks for the clarification.
If the molarities are all 1.0 mol/dm3, check the Data Booklet values. If the reduction potentials and standard potentials show feasibility, then redox will occur. Check if the cation, the anion, neither, or both, will react with the oxidizing agent.
Of course, the molarities are hardly ever 1.0 mol/dm3. Hence, if the question does not specify or provide sufficient information, make a reasonable educated assumption (and state your assumptions), and proceed with calculations accordingy.
In this case, based on Data Booklet values, and in the case of relatively similar enough molarities, you may justifiably assume that MnO4- is powerful enough to oxidize both cation and anion. Write two separate sets of half-equations to obtain two separate balanced redox equations, and proceed to calculate the required values based on the stoichiometry of the balanced redox equations.
Originally posted by Garrick_3658:Oh yeah, it applies to other cations with variable oxidation states too (copper, zinc, ... those oh-so-unstable-cations)
Aha!!! Gotcha!!! Zinc is NOT a transition metal and is does NOT exhibit variable oxidation states! Don't make this common student error of assuming it's a transition metal with variable O.S. just because it is a d-block element!