QJEEAdv15Chbd8a: JEE Advanced 2015 Chemistry - Class 12 JEEAdv15Chbd8a Solution: In dilute aqueous H 2 SO 4 , the complex…

In complex, $\mathop {{{[Fe{{({C_2}{O_4})}_2}{{({H_2}O)}_2}]}^{2 - }}}\limits_{Diaquodioxalatoferrate\,(II)}$ ,

Fe is in +2 oxidation state.

In acidic medium, $KMn{O_4}$ oxidises $F{e^{2 + }}$ to $F{e^{3 + }}$ ,

$2MnO_4^ - + 16{H^ + } + 10F{e^{2 + }} \to 2M{n^{2 + }} + 8{H_2}O + 10F{e^{3 + }}$

or $MnO_4^ - + 8{H^ + } + 5F{e^{2 + }} \to M{n^{2 + }} + 4{H_2}O + 5F{e^{3 + }}$

${{Rate\,of\,change\,of\,[{H^ + }]} \over {Rate\,of\,change\,of\,[MnO_4^ - ]}} = {8 \over 1} = 8$