The standard reduction potential (E°) values of $Ag^+|Ag, K^+|K, Mg^{2+}|Mg$ and $Cr^{3+}|Cr$ are 0.80 V, -2.93 V, -2.37 V and -0.74 V, respectively. The decreasing order of reducing power of the following metals is

(A) Ag
(B) K
(C) Mg
(D) Cr

Choose the correct answer from the options given below:

(B), (C), (D), (A)

The correct answer is Option (3) → (B), (C), (D), (A)

The reducing power of a metal is its tendency to lose electrons (get oxidized), i.e., act as a reducing agent.

The standard reduction potential (E°) given is for the half-reaction: Mⁿ⁺ + ne⁻ → M

• A more negative (or lower) E° means the reduction is less favorable → the reverse reaction (oxidation of metal) is more favorable → stronger reducing agent.
• A more positive (or higher) E° means the metal is weaker as a reducing agent.

Given E° values:

• Ag⁺/Ag: +0.80 V
• Cr³⁺/Cr: –0.74 V
• Mg²⁺/Mg: –2.37 V
• K⁺/K: –2.93 V

Decreasing order of reducing power (strongest → weakest): K > Mg > Cr > Ag

Corresponding to options: (B) K > (C) Mg > (D) Cr > (A) Ag

Thus, the correct choice is (B), (C), (D), (A).