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Electrochemical Series

Consider the ...

Question

Consider the cell at $25^{o} C$
$Z n | Z n^{2 +} (a q), (1 M) | | F e^{3 +} (a q), F e^{2 +} (a q) | P t (s)$
The fraction of total iron present as $F e^{3 +}$ ion at the cell potential of $1.500 V$ is $x \times 10^{- 2}$ . The value of $x$ is :
(Nearest integer)
Given:
$E_{F e^{3 +} / F e^{2 +}}^{0} = 0.77 V E_{Z n^{2 +} / Z n}^{0} = - 0.76 V$

24.0

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Solution

$Z n (s) | Z n^{2 +} (a q, 1 M) | | F e^{3 +} (a q), F e^{2 +} (a q) | P t (s)$

Net reaction :
$Z n (s) + 2 F e^{3 +} (a q) ⟶ Z n^{2 +} (a q) + 2 F e^{2 +} (a q)$

$Q = \frac{[Z n^{2 +}] [F e^{2 +}]^{2}}{[F e^{3 +}]^{2}}$

$E_{c e l l} = E_{c e l l}^{o} - \frac{0.0591}{n} l o g Q$

$1.500 = 1.53 - \frac{0.0591}{2} l o g {(\frac{[F e^{2 +}]}{[F e^{3 +}]})}^{2}$

$\frac{[F e^{2 +}]}{[F e^{3 +}]} = 3.218$

${Fraction of Fe}^{3 +} = \frac{1}{4.218} = 0.237 = 23.7 \times 10^{- 2}$

${Fraction of Fe}^{3 +} = 24 \times 10^{- 2} x = 24$

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Similar questions

25^{o} C

P t (s) | F e^{2 +} (a q, 0.1 M), F e^{3 +} (a q, 0.01 M); E_{F e^{3 +} / F e^{2 +}}^{0} = + 0.77 V

Z n (s) | Z n^{2 +} (a q) | | M^{x +} (a q) | M (s)

$M^{x +} (a q / M (s))$	$A u^{3 +} (a q) / A u (s)$	$A g^{+} / A g (s)$	$F e^{3 +} (a q) / F e^{2 +} (a q)$	$F e^{2 +} (a q) / F e (s)$
$E_{M^{x +} / M^{/ (V)}}^{o}$	$1.40$	$0.80$	$0.77$	$- 0.44$

E_{Z n^{2 +} / Z n}^{o} = - 0.76 V

E_{c e l l}^{o}

25^{o}

Z n^{2 +} (a q) + 2 e^{-} ⇌ Z n (s), - 0.76

C r^{3 +} (a q) + 3 e^{-} ⇌ C r (s), - 0.74

2 H^{+} (a q) + 2 e^{-} ⇌ H_{2} (g), + 0.0

F e^{3 +} (a q) + e^{-} ⇌ F e^{2 +} (a q), 0.77

E^{0}

F e^{3 +} (a q) + 3 e^{-} \to F e (s)

E^{0}

F e^{3 +} (a q) + e^{-} \to F e^{2 +} (a q); E^{0} = 0.77 V

F e^{2 +} (a q) + 2 e^{-} \to F e (s); E^{0} = - 0.44 V

298 K

{Z n}^{2 +} (a q) + 2 e^{-} ⇌ Z n (s) - 0.762

{C r}^{3 +} (a q) + 3 e^{-} ⇌ C r (s) - 0.74

2 H^{+} (a q) + 2 e^{-} ⇌ H_{2} (g) + 0.00

{F e}^{3 +} (a q) + e^{-} ⇌ {F e}^{2 +} (a q) + 0.77

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