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Application of Electrolysis

At 298 K, the...

Question

At 298 K, the standard reduction potentials for the following half-reactions are given. Which acts as an anode with others in an electrochemical cell?
$Z n^{+ 2} (a q) + 2 e^{-} \to Z n (s),$ -0.762 V
$C r^{+ 3} (a q) + 3 e^{-} \to C r (s),$ -0.740 V
$2 H^{+} (a q) + 2 e^{-} \to H_{2} (g),$ 0.000 V
$F e^{+ 3} (a q) + e^{-} \to F e^{2 +} (a q),$ +0.762 V

Z n (s)

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H_{2} (g)

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C r (s)

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F e^{2 +} (a q)

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Solution

The correct option is A $Z n (s)$
$E_{c e l l} = SRP of cathode - SRP of anode$
$∴$ To act as anode $E_{c e l l} > 0$
$∴$ SRP cathode > SRP of the anode (for all cases)
$∴$ The one with lowest SRP can act as an anode for all

$∴ Z n (S R P = - 0.76)$ acts as an anode.

Hence, option $A$ is correct.

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Similar questions

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

C r^{3 +} (a q) + 3 e^{-} ⇌ C r (s); - 0.740

2 H^{⨁} (a q) + 2 e^{-} ⇌ H_{2} (g); 0.000

F e^{3 +} (a q) + 3 e^{-} ⇌ F e^{2 +} (a q); 0.770

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

E^{\circ}

- 0.762 V

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

E^{\circ}

- 0.740 V

2 H_{(a q)}^{+} + 2 e^{-} ⇌ H_{2 (g)}

E^{\circ}

0.000 V

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

E^{\circ}

0.770 V

25^{\circ} C

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

C r^{3 +} (a q .) + 3 e^{-} ⇌ C r (s); - 0.740

2 H^{+} + 2 e^{-} ⇌ H_{2} (g); 0.00

F e^{3 +} + e^{-} ⇌ F e^{2 +}; 0.77

298 K

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

C r^{3 +} (a q) + 3 e ⇌ C r (s); - 0.740 V

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

F e^{3 +} (a q) + e ⇌ F e^{2 +} (a q); 0.770 V

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

C r^{3 +} (a q) + 2 e ⇌ C r (s) - 0.740

2 H^{+} (a q) + 2 e ⇌ H_{2} (g) 0.000

F e^{3 +} (a q) + 2 e ⇌ F e^{2 +} (a q) 0.770

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