KVPY Sample Paper KVPY Stream-SX Model Paper-5

In order to oxidise a mixture of one mole of each of \[Fe{{C}_{2}}{{O}_{4}},\] \[F{{e}_{2}}({{C}_{2}}{{O}_{4}})3,\] \[FeS{{O}_{4}}\] and \[F{{e}_{2}}{{(S{{O}_{4}})}_{3}}\] in acidic medium, the number of moles of \[KMn{{O}_{4}}\]required is :

A) 2

B) 1

C) 1.5

D) 3

Correct Answer: A

Solution :

\[{{F}_{e}}{{C}_{2}}{{O}_{4}}\to F{{e}^{+3}}+C{{O}_{2}}\]

\[F{{e}_{2}}{{({{C}_{2}}{{O}_{4}})}_{3}}\to C{{O}_{2}}\]

\[F{{e}_{2}}{{(S{{O}_{4}})}_{3}}\to \,No\,oxidation\]

\[FeS{{O}_{4}}\to F{{e}^{+3}}\]

\[{{g}_{m}}E\,(KMn{{O}_{4}})={{g}_{m}}E\,(Fe{{C}_{2}}{{O}_{4}})+{{g}_{m}}E\,\,[F{{e}_{2}}{{({{C}_{2}}{{O}_{4}})}_{3}}]+{{g}_{m}}E\,(FeS{{O}_{4}})\]

\[moles\,\times \,V.F=moles\times V.F.+moles\times V.F.+moles\times V.F.\]

\[x\times 5=(1\times 3)+(1\times 6)+(1\times 1)\]

\[5x=10\,(MnO_{4}^{-}\to M{{n}^{+2}})\]

\[x=2.\]