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Electrode Potential

Standard elec...

Question

Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox titrations. Some half cell reactions and their standard potentials are given below:
$M n O_{4}^{-} (a q .) + 8 H^{+} (a q .) + 5 e^{-} \to M n^{2 +} (a q .) + 4 H_{2} O (l); E^{o} = 1.51 V$
$C r_{2} O_{7}^{2 -} (a q .) + 14 H^{+} (a q .) + 6 e^{-} \to 2 C r^{3 +} (a q .) + 7 H_{2} O (l); E^{o} = 1.38 V$
$F e^{3 +} (a q .) + e^{-} \to F e^{2 +} (a q .); E^{o} = 0.77 V$
$C l_{2} (g) + 2 e^{-} \to 2 C l^{-} (a q .); E^{o} = 1.40 V$
Identify the only incorrect statement regarding the quantitative estimation of aqueous $F e (N O_{3})_{2}$ .

A

M n O_{4}^{-}

can be used in aqueous HCl.

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B

C r O_{7}^{2 -}

can be used in aqueous HCl.

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C

M n O_{4}^{-}

can be used in aqueous

H_{2} S O_{4}

.

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D

C r O_{7}^{2 -}

can be used in aqueous

H_{2} S O_{4}

.

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Solution

The correct option is A $M n O_{4}^{-}$ can be used in aqueous HCl.
$M n O_{4}^{-}$ will oxidise $C l^{-}$ ion according to equation,

$M n^{7 +} + 5 e \to M n^{2 +}$
$2 C l^{-} \to C l_{2} + 2 e$
Thus, $E_{c e l l}^{o} = E_{O P_{C l^{-}} / C l^{2}}^{o} + E_{R P_{M n O_{4}^{-}} / M n^{2 +}}^{o}$

$= - 1.40 + 1.51 = 0.11 V$
or reaction is feasible $M n O_{4}^{-}$ will oxidise $F e^{2 +}$ to $F e^{3 +}$
$M n^{7 +} + 5 e \to M n^{2 +}$
$F e^{2 +} \to F e^{3 +} + e$
$∴ E_{c e l l}^{o} = E_{O P_{F e^{2 +} / F e^{3 +}}}^{o} + E_{M n O_{4}^{-} / M n^{2 +}}$
$= - 0.77 + 1.51$
$= 0.74 V$ or reaction is feasible
Thus, $M n O_{4}^{-}$ will not only oxidise $F e^{2 +}$ to $F e^{3 +}$ in aqueous HCl medium but it will also oxidise $C l^{-}$ to $C l_{2}$ . Suitable oxidant should not oxidise $C l^{-}$ to $C l_{2}$ and should only oxidise $f e^{2 +}$ to $F e^{3 +}$ in redox titrations.
So $M n O_{4}^{-}$ can not be used in aqueous HCl.

Hence,option A is correct.

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Similar questions

Q. Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox Titration. Some half – cell reactions and their standard potential are given below:

M n O_{4}^{-} (a q) + 8 H^{+} (a q) + 5 e^{-} \to M n^{2 +} (a q) + 4 H_{2} O (I); E^{\circ} = 1.51 V

C r_{2} O_{7}^{2 -} (a q) + 14 H^{+} (a q) + 6 e^{-} \to 2 C r^{3 +} (a q) + 7 H_{2} O (I); E^{\circ} = 1.38 V

F e^{3 +} (a q) + e^{-} \to F e^{2 +} (a q); E^{\circ} = 0.77 V

C l_{2} (g) + 2 e^{-} \to 2 C l^{-} (a q); E^{\circ} = 1.40 V

Identify the only incorrect statement regarding the quantitative estimation of aqueous

F e (N O_{3})_{2}

.

Q. Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox Titration. Some half – cell reactions and their standard potential are given below:

M n O_{4}^{-} (a q) + 8 H^{+} (a q) + 5 e^{-} \to M n^{2 +} (a q) + 4 H_{2} O (I); E^{\circ} = 1.51 V

C r_{2} O_{7}^{2 -} (a q) + 14 H^{+} (a q) + 6 e^{-} \to 2 C r^{3 +} (a q) + 7 H_{2} O (I); E^{\circ} = 1.38 V

F e^{3 +} (a q) + e^{-} \to F e^{2 +} (a q); E^{\circ} = 0.77 V

C l_{2} (g) + 2 e^{-} \to 2 C l^{-} (a q); E^{\circ} = 1.40 V

Identify the only incorrect statement regarding the quantitative estimation of aqueous

F e (N O_{3})_{2}

.

Q. Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox titration. Some half-cell reactions and their standard potentials are given below:

M n O_{4}^{-} (a q .) + 8 H^{+} (a q .) + 5 e^{-} \to M n^{2 +} (a q .) + 4 H_{2} O (l); E^{\circ} = 1.51 v o l t

C r_{2} O_{7}^{2 -} (a q .) + 14 H^{+} (a q .) + 6 e^{-} \to 2 C r^{3 +} (a q .) + 7 H_{2} O (l)^{'} E^{\circ} = 1.38 v o l t

F e^{3 +} (a q .) + e^{-} \to F e^{2 +} (a q .); E^{\circ} = 0.77 v o l t

C l_{2} (g) + 2 e^{-} \to 2 C l^{-} (a q .); E^{\circ} = 1.40 v o l t

Identity the only incorrect statement regarding the quantitative estimation of aqueous

F e (N O_{3})_{2}

.

Q. Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox titration. Some half cell reactions and their standard potentials are given below.

M n_{4}^{-} (a q) + 8 H^{+} (a q) + 5 e^{-} \to M n^{2 +} (a q) + 4 H_{2} O (l); E^{\circ} = 1.51 V

C r_{2} O_{7}^{2 -} (a q) + 14 H^{+} + 6 e^{-} \to 2 C r^{3} + (a q) + 7 H_{2} O (l); E^{\circ} = 138 V

F e^{3 +} (a q) + e^{-} \to F e^{2 +} (a q); E^{\circ} = 0.77 V

C l_{2} (g) + 2 e^{-} \to 2 C l^{-} (a q); E^{\circ} = 1.40 V

Identify the incorrect statement regarding the quantitative estimation of gaseous

F e (N O_{3})_{2}

.

Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox Titration. Some half – cell reactions and their standard potential are given below:
$M n O_{4}^{-} (a q) + 8 H^{+} (a q) + 5 e^{-} \to M n^{2 +} (a q) + 4 H_{2} O (I); E^{\circ} = 1.51 V$
$C r_{2} O_{7}^{2 -} (a q) + 14 H^{+} (a q) + 6 e^{-} \to 2 C r^{3 +} (a q) + 7 H_{2} O (I); E^{\circ} = 1.38 V$
$F e^{3 +} (a q) + e^{-} \to F e^{2 +} (a q); E^{\circ} = 0.77 V$
$C l_{2} (g) + 2 e^{-} \to 2 C l^{-} (a q); E^{\circ} = 1.40 V$

Identify the only incorrect statement regarding the quantitative estimation of aqueous $F e (N O_{3})_{2}$ .

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