Standard reduction electrode potential of four metals A, B, C and D are as follows. The correct order of decreasing strength of reducing power is:
A. Metal A = +0.5 V
B. Metal B = -3.0 V
C. Metal C = -1.2 V
D. Metal D = -2.3 V
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → B > D > C > A
The given values are standard reduction potentials. The more negative the E°, the less the metal ion tends to be reduced and the more readily the metal itself loses electrons, so the stronger the metal is as a reducing agent.
(B) Metal B = −3.0 V — first, the strongest reducing agent: its E° is the most negative.
(D) Metal D = −2.3 V — second: less negative than B, more negative than C.
(C) Metal C = −1.2 V — third: still negative, so it gives electrons more readily than hydrogen, but less readily than B and D.
(A) Metal A = +0.5 V — last, the weakest reducing agent: its E° is positive, so its ion is readily reduced and the metal holds its electrons.
NCERT (2026-27 edition):
Measurement of Electrode Potential – …
