Standard reduction electrode potentials of three metals A,B and C are $+ 0.5 V, - 3.0 V & - 1.2 V$ respectively.
The decreasing order of reducing powers of these metals is:

A > B > C

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C > B > A

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A > C > B

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B > C > A

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Solution

The correct option is D $B > C > A$
Higher the standard reduction potential (SRP) of the metal, more is the tendency of that metal to get reduced, and hence lower is its reducing power.
Order of SRP:
$A > C > B$
So, the order of reducing power is $B > C > A$ .
Hence, Option (d) is correct.

Theory: $Electrochemical Series$

$Half-Reaction$ Standard Reduction Potential $E^{\circ}$ (at 298 K)

$F_{2} (g) + 2 e^{-} \to 2 F^{-} (a q)$ $+ 2.87 V$

$M n O_{4} (a q) + 8 H^{+} (a q) + 5 e^{-} \to M n^{2 +} (a q) + 4 H_{2} O (l)$
$+ 1.51 V$

$A u^{3 +} (a q) + 3 e^{-} \to A u (s)$ $+ 1.4 V$

$2 H g^{2 +} (a q) + 2 e^{-} \to H g^{2 +} (a q)$ $+ 0.92 V$

$A g^{+} (a q) + e^{-} \to A g (s)$ $+ 0.8 V$

$C u^{2 +} (a q) + 2 e^{-} \to C u (s)$ $+ 0.34 V$

$2 H^{+} (a q) + 2 e^{-} \to H_{2} (g)$ $0 V$

$P b^{2 +} (a q) + 2 e^{-} \to P b (s)$ $- 0.13 V$

$S n^{2 +} (a q) + 2 e^{-} \to S n (s)$ $- 0.14 V$

$N i 2 + (a q) + 2 e^{-} \to N i (s)$ $- 0.25 V$

$F e^{2 +} (a q) + 2 e^{-} \to F e (s)$ $- 0.44 V$

$Z n^{2 +} (a q) + 2 e^{-} \to Z n (s)$ $- 0.76 V$

$A l^{3 +} (a q) + 3 e^{-} \to A l (s)$ $- 1.66 V$

$M g^{2 +} (a q) + 2 e^{-} \to M g (s)$ $- 2.36 V$

$N a^{+} (a q) + e^{-} \to N a (s)$ $- 2.71 V$

$C a^{2 +} (a q) + 2 e^{-} \to C a (s)$ $- 2.87 V$

$K^{+} (a q) + e^{-} \to K (s)$ $- 2.93 V$

$L i^{+} (a q) + e^{-} \to L i (s)$ $- 3.05 V$

Down the table, as the SRP decreases, the reducing power increases.

Suggest Corrections

Similar questions

A, B

C

+ 0.5 V, - 3.0 V

+ 1.2 V

X

Y

Z

- 1.2 V

+ 0.5 V

- 3.0 V

E^{\circ}

The standard reduction potential of three metals $X, Y, Z$ are $0.52, 3.03$ and $1.18 V$ respectively.

The order of reducing power of the corresponding metals is:

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$Half-Reaction$	Standard Reduction Potential $E^{\circ}$ (at 298 K)
$F_{2} (g) + 2 e^{-} \to 2 F^{-} (a q)$	$+ 2.87 V$
$M n O_{4} (a q) + 8 H^{+} (a q) + 5 e^{-} \to M n^{2 +} (a q) + 4 H_{2} O (l)$	$+ 1.51 V$
$A u^{3 +} (a q) + 3 e^{-} \to A u (s)$	$+ 1.4 V$
$2 H g^{2 +} (a q) + 2 e^{-} \to H g^{2 +} (a q)$	$+ 0.92 V$
$A g^{+} (a q) + e^{-} \to A g (s)$	$+ 0.8 V$
$C u^{2 +} (a q) + 2 e^{-} \to C u (s)$	$+ 0.34 V$
$2 H^{+} (a q) + 2 e^{-} \to H_{2} (g)$	$0 V$
$P b^{2 +} (a q) + 2 e^{-} \to P b (s)$	$- 0.13 V$
$S n^{2 +} (a q) + 2 e^{-} \to S n (s)$	$- 0.14 V$
$N i 2 + (a q) + 2 e^{-} \to N i (s)$	$- 0.25 V$
$F e^{2 +} (a q) + 2 e^{-} \to F e (s)$	$- 0.44 V$
$Z n^{2 +} (a q) + 2 e^{-} \to Z n (s)$	$- 0.76 V$
$A l^{3 +} (a q) + 3 e^{-} \to A l (s)$	$- 1.66 V$
$M g^{2 +} (a q) + 2 e^{-} \to M g (s)$	$- 2.36 V$
$N a^{+} (a q) + e^{-} \to N a (s)$	$- 2.71 V$
$C a^{2 +} (a q) + 2 e^{-} \to C a (s)$	$- 2.87 V$
$K^{+} (a q) + e^{-} \to K (s)$	$- 2.93 V$
$L i^{+} (a q) + e^{-} \to L i (s)$	$- 3.05 V$