Galvanic Cell Conceptual Question

blueblueblue

1. The problem statement, all variables and given/known data

In a galvanic cell, the electrode that builds up a precipitate of metal (known as plating out) is:
A. the cathode, and its surface is rich in positive charge.
B. the anode, and its surface is rich in positive charge.
C. the cathode, and its surface is rich in electrons.
D. the anode, and its surface is rich in electrons.

2. Relevant equations
----N/A----

3. The attempt at a solution

I guess my dilemma revolves around the solution that the book gave. The book: "Answer C. The cathode is defined as the electrode at which reduction occurs. This eliminates choices B and D. Metal cations are converted into metal at the cathode. For a cation to be converted into a metal, it must gain electrons (undergo reduction), so the surface of the cathode must be rich in electrons."

I understand that reduction and metal plating occurs at the cathode, my problem is the second part of the answer. Wouldn't the cathode be rich in positive charge? My understanding is that the cathode contains the metal cations, which will eventually pick up the electrons coming from the anode. I can also understand that the cathode would gather electrons on its surface so that metal cations can pick them up. However, I'm more inclined to pick A than C. Please help! Thanks in advance.

Borek

Would be positively charged cathode able to attract cations?

Cathode doesn't contain metal cations, they get reduced the moment they touch the surface.

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blueblueblue

Oh, so are the metal cations usually in solution? I was always under the assumption that the cathode was a metal plate containing the metal cations. At least that's what it looks like every time I see a simple diagram of a galvanic cell.

So is the cathode electrode just a conductor allowing electrons to gather on its surface, which attracts metal cations from the cathode solution allowing reduction to occur?

Thanks for your response!

Borek

Both electrodes are just conductors, surrounded by ions. Reaction takes place only at the surface (phase boundary).

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blueblueblue

Awesome! Answered all my questions. Thanks again, Borek!