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Electrochemical Series

The standard ...

Question

The standard reduction potentials at $298 K$ for the following half-cell reactions are given by
${Z n}^{2 +} (a q) + 2 e^{-} ⇌ Z n (s) - 0.762$
${C r}^{3 +} (a q) + 3 e^{-} ⇌ C r (s) - 0.74$
$2 H^{+} (a q) + 2 e^{-} ⇌ H_{2} (g) + 0.00$
${F e}^{3 +} (a q) + e^{-} ⇌ {F e}^{2 +} (a q) + 0.77$
Which one of the following is the strongest reducing agent?

Z n (s)

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C r (s)

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H_{2} (s)

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

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Solution

The correct option is A $Z n (s)$
The metals having higher negative value of standard reduction potential are placed above hydrogen in electrochemical series. The metals placed above hydrogen has a great tendency to donate electrons or oxidising power. The metals having great oxidising power are strongest reducing agent. $Z n$ has higher negative value of standard reduction potential. Therefore, it is the strongest reducing agent.

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Similar questions

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) + 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^{2 +} (a q) + 2 e^{-} ⇌ Z n (s);

- 0.762 V

C r^{3 +} (a q) + 3 e^{-} ⇌ C r (s);

- 0.74 V

2 H^{+} (a q) + 2 e^{-} ⇌ H_{2} (g);

+ 0.00 V

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

+ 0.77 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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