JEE Main 2016 · Chemistry · Redox Reactions and Titrations · medium

A 1.44 g sample of pure FeC2O4 (M=144) is titrated in acidic medium with 0.040 M KMnO4. In the reaction both Fe^2+ and C2O4^2- are oxidised…

Single correct option

1.44\ \mathrm{g}

sample of pure

\mathrm{FeC_2O_4}

(

M=144

) is titrated in acidic medium with

0.040\ \mathrm{M}

\mathrm{KMnO_4}

. In the reaction both

\mathrm{Fe^{2+}}

and

\mathrm{C_2O_4^{2-}}

are oxidised completely (to

\mathrm{Fe^{3+}}

and

\mathrm{CO_2}

). The volume of

\mathrm{KMnO_4}

solution required is

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Answer: (C) $150\ \mathrm{mL}$

Moles of

\mathrm{FeC_2O_4}=1.44/144=0.010

. Electrons lost per formula unit:

\mathrm{Fe^{2+}\to Fe^{3+}}

gives 1 and

\mathrm{C_2O_4^{2-}\to 2CO_2}

gives 2, so the n-factor is 3, i.e.

0.030

equivalents. In acid,

\mathrm{MnO_4^-\to Mn^{2+}}

has n-factor 5, so moles of permanganate

=0.030/5=0.0060

. Volume

=0.0060/0.040=0.150

=150

mL. Counting only iron (n=1) gives 50 mL, only oxalate gives 100 mL, and a 1:1 mole ratio gives 250 mL.

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