Question

I am reading about electrochemical cells from the chapter: Electrochemical cells, Batteries and Fuel cells in the book 'Physical Chemistry' by Thomas Engel and Philip Reid, 3rd edition. I came across the following paragraph and I want to know if my understanding of this paragraph is correct or not? The paragraph is about Zn elctrode partially immersed in an aqueous solution of ZnSO4

Paragraph: Can we measure Φ
( half-cell potential) directly? Let us assume we can carry out the measurement using two chemically inert Pt wires as probes. One Pt wire is placed on Zn electrode and the second Pt wire is placed in the ZnSO4 solution. However, the measured voltage is the difference in electrical potential between a Pt wire connected to a zinc electrode in ZnSO4 solution and a Pt electrode in a ZnSO4 solution, which is not what we want.
My question is whether the author wants to say that the second platinum wire will act as an electrode in zinc sulphate solution and hence the potential difference measured will be between zinc electrode and platinum wire which won't be the potential difference between zinc electrode and zinc sulphate solution?

Answer 1

The author is discussing the measurement of the half-cell potential using two Pt wires as probes. The measured potential difference is between the Zn electrode and the Pt wire, not between the Zn electrode and the ZnSO4 solution.

Step-by-step explanation:

The paragraph you provided is discussing the measurement of the half-cell potential (Φ) using two chemically inert Pt wires as probes. One Pt wire is placed on the Zn electrode and the second Pt wire is placed in the ZnSO4 solution.

The author is saying that when the voltage is measured, it would be the difference in electrical potential between the Pt wire connected to the Zn electrode and the Pt wire connected to the ZnSO4 solution, which is not the potential difference between the Zn electrode and the ZnSO4 solution.

Therefore, the author wants to convey that the second Pt wire will act as an electrode in the zinc sulfate solution, and the measured potential difference will be between the zinc electrode and the Pt wire, not between the zinc electrode and the zinc sulfate solution.