Match List-I with List-II.
| List-I (Half-cell reaction) | List-II (E°/V at 298 K) |
|---|---|
| (A) \( \ce{F2(g) + 2e^- -> 2F^-} \) | (I) −0.76 |
| (B) \( \ce{Ag+ + e^- -> Ag(s)} \) | (II) 2.87 |
| (C) \( \ce{Zn^2+ + 2e^- -> Zn(s)} \) | (III) −3.05 |
| (D) \( \ce{Li+ + e^- -> Li(s)} \) | (IV) 0.80 |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-II, B-IV, C-I, D-III
Standard electrode potentials are measured against the standard hydrogen electrode (E° = 0). The higher the E°, the greater the tendency of the oxidised form to be reduced; a negative E° means the metal reduces H+ ions more easily than hydrogen does.
(A) \( \ce{F2(g) + 2e^- -> 2F^-} \) — This matches (II) 2.87. Fluorine has the highest E° in the series; F2 is the strongest oxidising agent.
(B) \( \ce{Ag+ + e^- -> Ag(s)} \) — This matches (IV) 0.80. The value is positive, so Ag+ ions are reduced more easily than H+ ions.
(C) \( \ce{Zn^2+ + 2e^- -> Zn(s)} \) — This matches (I) −0.76. The value is negative: hydrogen ions can oxidise zinc.
(D) \( \ce{Li+ + e^- -> Li(s)} \) — This matches (III) −3.05. Lithium has the lowest E°; lithium metal is the most powerful reducing agent in aqueous solution.
NCERT (2026-27 edition):
2.2.1 Measurement of Electrode Potential – “Similarly, the measured emf of the cell: Pt(s) H2(g, 1 bar) H+ (aq, 1 M) Zn2+ (aq, 1M) Zn is –0.76 V corresponding to the standard electrode potential of the half-cell reaction: Zn2+ (aq, 1 M) + 2e– → Zn(s)”
“…The values of standard electrode potentials for some selected half-cell reduction reactions are given in Table 2.1. … It can be seen that the standard electrode potential for fluorine is the highest in the Table indicating that fluorine gas (F2) has the maximum tendency to get reduced to fluoride ions (F–) and therefore fluorine gas is the strongest oxidising agent and fluoride ion is the weakest reducing agent. Lithium has the lowest electrode potential indicating that lithium ion is the weakest oxidising agent while lithium metal is the most powerful reducing agent in an aqueous solution.”
Table 2.1: Standard Electrode Potentials at 298 K
