Question

Which of the following is a half-reaction?

• A. Zn + Cu²⁺→ Zn²⁺ +Cu
• B. H⁺ OH^-→H₂O
• C. Ag⁺+e^-→Ag
• D. Ag⁺+Cl^-→AgCI

Answer 1

The Correct Option is C

To identify which of the given reactions is a half-reaction, we need to understand what constitutes a half-reaction. A half-reaction is a part of the redox (reduction-oxidation) process and can be either an oxidation half-reaction or a reduction half-reaction.

In a half-reaction:

• An oxidation half-reaction involves the loss of electrons.
• A reduction half-reaction involves the gain of electrons. 

Let's analyze each option:

1. \(Zn + Cu^{2+} \rightarrow Zn^{2+} + Cu\): This is a full redox reaction composed of both oxidation and reduction. Zinc oxidizes while copper reduces, so this is not a half-reaction.
2. \(H^{+} + OH^{-} \rightarrow H_2O\): This is a neutralization reaction between an acid and a base, forming water. It is not a redox reaction, hence not a half-reaction.
3. \(Ag^{+} + e^{-} \rightarrow Ag\): This equation represents the gain of one electron by silver ion to form silver metal. It is a reduction half-reaction.
4. \(Ag^{+} + Cl^{-} \rightarrow AgCl\): This is a precipitation reaction where silver ions react with chloride ions to form silver chloride. It is not a half-reaction as it does not involve transfer of electrons in a redox sense.

Therefore, the correct half-reaction from the given options is \(Ag^{+} + e^{-} \rightarrow Ag\).