JEE Advanced 2024 Paper 2 · Chemistry · Redox Reactions and Titrations · medium

A solid mixture contains 0.010 mol of FeC2O4 and 0.010 mol of Fe2(C2O4)3. It is dissolved in dilute H2SO4 and titrated with 0.020 M KMnO4 (reduced to…

Numerical answer

A solid mixture contains

0.010

mol of

\mathrm{FeC_2O_4}

and

0.010

mol of

\mathrm{Fe_2(C_2O_4)_3}

. It is dissolved in dilute

\mathrm{H_2SO_4}

and titrated with

0.020\ \mathrm{M}

\mathrm{KMnO_4}

(reduced to

\mathrm{Mn^{2+}}

). The volume of the permanganate solution consumed, in mL, is

Show answer and solution

Answer: 900

Work with equivalents. In acid

\mathrm{MnO_4^-}

is reduced to

\mathrm{Mn^{2+}}

(

n=5

), so 0.020 M

\mathrm{KMnO_4}

0.100\ \mathrm{eq\,L^{-1}}

. Oxidation by permanganate:

\mathrm{FeC_2O_4}

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

(1 e

^-

) and

\mathrm{C_2O_4^{2-}\to2CO_2}

(2 e

^-

), so

n

-factor

=3

\mathrm{Fe_2(C_2O_4)_3}

: iron is already

\mathrm{Fe^{3+}}

, only three oxalate ions are oxidised,

n

-factor

=3\times2=6

. Total equivalents of reductant

=0.010\times3+0.010\times6=0.090

eq. Volume of

\mathrm{KMnO_4}

=0.090/0.100=0.90

=900

mL.

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