7.How many moles of potassium permanganate are required to oxidise 3 mol potassium iodide?
Answers
You gots a couple of redox processes going on here…
Ferrous ion is OXIDIZED to ferric ion, i.e. Fe3+ …
Fe2+→Fe3++e−
Oxalate dianion is OXIDIZED to carbon dioxide… C(+III)→C(+IV)
−O(O=)C−C(=O)O−→2CO2(g)+2e−
We combine the oxidation reactions for simplicity…
Fe2+(C2O4)2−(aq)→Fe3++2CO2(g)+3e−
And this, I think, is balanced with respect to mass and charge, as is ABSOLUTELY required…
Meanwhile we ASSUME that permanganate ion is REDUCED to colourless Mn2+ ion…
MnO−4+8H++5e−→Mn2++4H2O(l)purple to colourless
And so we add FIVE of the former to THREE of the latter to remove the electrons, virtual particles of convenience…
5Fe2+(C2O4)2−(aq)+3MnO−4+24H++15e−→5Fe3++10CO2(g)+15e−+3Mn2++12H2O(l)
And we cancel away…
5Fe2+(C2O4)2−(aq)+3MnO−4+24H+→5Fe3++10CO2(g)+3Mn2++12H2O(l)
…which I think is balanced with respect to mass, and charge, but it is your problem, and you will have to check it for arithmetic error.
And thus one equiv ferrous ion requires 35 equiv of permanganate oxidant…