Question

The standard electrode potentials of Zn, Ag and Cu are -0.76, +0.80 and +0.34 V respectively. Identify the correct statement from the following.

• A. Ag can oxidize Zn and Cu
• B. Ag can reduce Zn\(^{2+}\) and Cu\(^{2+}\)
• C. Zn can reduce Ag\(^+\) and Cu\(^{2+}\)
• D. Cu can oxidize Zn and Ag

Hint:

A simple rule to remember is: a metal can "displace" or reduce the ions of any metal below it in the reactivity series (or above it in the standard potential series).
Here, Zn is the most reactive, so it can reduce both Cu\(^{2+}\) and Ag\(^+\).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
We are given standard reduction potentials (E°) for three metals. We must determine which statement about their spontaneous redox behavior is correct.

Step 2: Key Formula or Approach:
The standard reduction potential (E°) measures the tendency for a species to be reduced.
- A more negative E° indicates a stronger reducing agent (the metal is more easily oxidized).
- A more positive E° indicates a stronger oxidizing agent (the ion is more easily reduced).
A metal can spontaneously reduce the ions of another metal that has a more positive E°.

Step 3: Detailed Explanation:
Let's list the potentials in increasing order to create an electrochemical series:
E°(Zn\(^{2+}\)/Zn) = -0.76 V
E°(Cu\(^{2+}\)/Cu) = +0.34 V
E°(Ag\(^+\)/Ag) = +0.80 V
This order establishes the relative strengths:
- Strength as

reducing agents (metals): Zn $\gt $ Cu $\gt $ Ag.
- Strength as

oxidizing agents (ions): Ag\(^+\) $\gt $ Cu\(^{2+}\) $\gt $ Zn\(^{2+}\).
Now, let's evaluate each statement:
-

(A) Ag can oxidize Zn and Cu: Incorrect. The metal Ag is a reducing agent. Its ion, Ag\(^+\), is an oxidizing agent.
-

(B) Ag can reduce Zn\(^{2+}\) and Cu\(^{2+}\): Incorrect. Ag is the weakest reducing agent and cannot reduce ions of metals with lower (more negative) E° values.
-

(C) Zn can reduce Ag\(^+\) and Cu\(^{2+}\): Correct. Zn is the strongest reducing agent. Its E° is the most negative, so it can spontaneously reduce the ions of both Cu and Ag, which have more positive E° values.
-

(D) Cu can oxidize Zn and Ag: Incorrect. The metal Cu is a reducing agent. Its ion, Cu\(^{2+}\), can oxidize Zn but not Ag.

Step 4: Final Answer:
The correct statement is "Zn can reduce Ag\(^+\) and Cu\(^{2+}\)".