Which of the following statements are correct with reference to the following reaction?
\( \text{Zn}(s)+\text{Cu}^{2+}(aq)\rightarrow\text{Zn}^{2+}(aq)+\text{Cu}(s) \)
(A) The reduction reaction is \( \text{Cu}^{2+}(aq)+2e^{-}\rightarrow\text{Cu}(s) \)
(B) The oxidation reaction is \( \text{Zn}(s)\rightarrow\text{Zn}^{2+}(aq)+2e^{-} \)
(C) The two half (oxidation and reduction) reactions constitute redox couple.
(D) The given reaction is not a redox reaction.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B) and (C) only
A redox reaction is one in which one species is oxidised (loses electrons) and another is reduced (gains electrons) at the same time. It can be split into an oxidation half reaction and a reduction half reaction, which add up to the whole reaction. In the given reaction, the reaction of the Daniell cell, zinc goes from 0 to +2 (oxidation) and copper from +2 to 0 (reduction).
(A) The reduction reaction is \( \ce{Cu^2+(aq) + 2e- -> Cu(s)} \) — Correct. \( \ce{Cu^2+} \) gains two electrons; its oxidation state falls from +2 to 0.
(B) The oxidation reaction is \( \ce{Zn(s) -> Zn^2+(aq) + 2e-} \) — Correct. Zinc loses two electrons; its oxidation state rises from 0 to +2.
(C) The two half (oxidation and reduction) reactions constitute redox couple. — Correct. Each half reaction takes place in its own half-cell, and these half-cells, \( \ce{Zn^2+}/\ce{Zn} \) and \( \ce{Cu^2+}/\ce{Cu} \), are called redox couples.
(D) The given reaction is not a redox reaction. — Incorrect. Electrons pass from zinc to copper ions, so oxidation and reduction occur together; it is a redox reaction.
NCERT (2026-27 edition):
Galvanic Cells – “… Daniell cell discussed earlier is one such cell in which the following redox reaction occurs.
\( \ce{Zn(s) + Cu^2+(aq) -> Zn^2+(aq) + Cu(s)} \)
This reaction is a combination of two half reactions whose addition gives the overall cell reaction:
(i) \( \ce{Cu^2+ + 2e- -> Cu(s)} \) (reduction half reaction)
(ii) \( \ce{Zn(s) -> Zn^2+ + 2e-} \) (oxidation half reaction)
These reactions occur in two different portions of the Daniell cell. The reduction half reaction occurs on the copper electrode while the oxidation half reaction occurs on the zinc electrode. These two portions of the cell are also called half-cells or redox couples.”