Question

If a sample of iron and a sample of zinc come into contact, the zinc corrodes but the iron does not. If a sample of iron comes into contact with a sample of copper, the iron corrodes but the copper does not. Explain this phenomenon.

a) Zinc has a higher standard reduction potential
b) Copper forms a protective oxide layer
c) Iron displaces zinc in a redox reaction
d) Copper accelerates iron corrosion

Answer 1

Iron and zinc come into contact; zinc corrodes due to a more negative standard reduction potential, acting as the sacrificial anode. When iron contacts copper, iron corrodes as it has a lower reduction potential, with copper acting as the cathode, resisting corrosion. The correct option is A.

Step-by-step explanation:

When iron and zinc come into contact, zinc corrodes while iron does not. This is because zinc has a more negative standard reduction potential, indicating that it is more easily oxidized, and hence zinc serves as the sacrificial anode to the iron. Therefore, zinc corrodes in preference to iron.

Conversely, when iron comes into contact with copper, the iron corrodes but the copper does not. This is due to the fact that copper has a positive standard reduction potential and is less easily oxidized than iron. As a result, iron acts as the anode and corrodes, while copper acts as the cathode and does not corrode.

This phenomenon is explained by the concept of galvanic corrosion, which occurs when two dissimilar metals are in direct contact. The more active metal (with a more negative standard reduction potential) corrodes, serving as the anode, while the less active metal acts as the cathode.