Question

Which among the following is an example of Metal - metal ion electrode?

• A. Fe\(^{3+}\) (aq.) | Fe\(^{2+}\) (aq.) | Pt
• B. Cl\(^{-}\) (aq.) | AgCl(s) | Ag
• C. Zn\(^{2+}\) (aq.) | Zn(s)
• D. OH\(^{-}\) (aq.) | O\(_2(g)\), PO\(_2\) | Pt

Hint:

In a metal - metal ion electrode, the metal is in equilibrium with its ion in solution. Zn\(^{2+}\) | Zn is a classic example of this.

Answer 1

The Correct Option is C

Step 1: Understanding metal - metal ion electrode.
A metal - metal ion electrode consists of a metal and its ion in equilibrium, with the metal electrode immersed in a solution of its own ions. The electrode potential is determined by this equilibrium.
Step 2: Analyzing the options.
(A) Fe\(^{3+}\) (aq.) | Fe\(^{2+}\) (aq.) | Pt: This is a metal - metal ion electrode, but it involves a platinum electrode because iron is in different oxidation states. It is a valid electrode but not the best example.
(B) Cl\(^{-}\) (aq.) | AgCl(s) | Ag: This is a metal - salt electrode, not a metal - metal ion electrode.
(C) Zn\(^{2+}\) (aq.) | Zn(s): This is a typical metal - metal ion electrode where zinc metal is in equilibrium with zinc ions.
(D) OH\(^{-}\) (aq.) | O\(_2(g)\), PO\(_2\) | Pt: This is a gas - metal ion electrode, not a metal - metal ion electrode.
Step 3: Conclusion.
The correct answer is (C) Zn\(^{2+}\) (aq.) | Zn(s), as it is the best example of a metal - metal ion electrode.