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Application of Electrolysis

The standard ...

Question

The standard reduction potentials at $25^{\circ} C$ for the following half reactions are given against each;
$Z n^{2 +} (a q .) + 2 e^{-} ⇌ Z n (s); - 0.762$
$C r^{3 +} (a q .) + 3 e^{-} ⇌ C r (s); - 0.740$
$2 H^{+} + 2 e^{-} ⇌ H_{2} (g); 0.00$
$F e^{3 +} + e^{-} ⇌ F e^{2 +}; 0.77$
Which is the strongest reducing agent?

Z n

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C r

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H_{2} (g)

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F e^{2 +} (a q .)

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Solution

The correct option is A $Z n$
Lesser the standard reduction potential i.e. more it is negative, more tendency to undergo oxidation so better will be the reducing property.
$E_{Z n^{2 +} / Z n}^{o}$ i.e. standard reduction potential of $Z n$ is least among all four so it is best reducing agent among these four.

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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

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

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

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

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

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