Which property primarily determines which metal becomes the anode in a galvanic couple?

• A. The color of the metal.
• B. The metal with the higher electrical conductivity.
• C. The relative nobility as indicated by electrode potential.
• D. The surface roughness.

Answer: (C)

The key idea is that in a galvanic couple, the metal that is less noble—its electrode potential is lower or more negative—will oxidize first and become the anode, while the more noble metal with a higher electrode potential serves as the cathode. This difference in electrode potentials drives a spontaneous redox reaction: the anode loses electrons, and those electrons flow to the cathode where reduction occurs. So the primary property is the relative nobility indicated by electrode potentials. For example, zinc (less noble, more negative potential) tends to oxidize in contact with copper (more noble, higher potential), making zinc the anode and copper the cathode. The other factors listed—color, higher electrical conductivity, and surface roughness—do not determine which metal becomes the anode; they may influence corrosion behavior in other ways but not the fundamental thermodynamic preference for oxidation.