Corrosion And Electrochemical Reactions

To evaluate the given statements about corrosion, let's analyze each statement individually.

Statement I: "Corrosion is an electrochemical phenomenon in which pure metal acts as an anode and impure metal as a cathode."

Corrosion is indeed an electrochemical process. However, the statement about pure and impure metal roles is misleading. Corrosion involves the flow of electrons from the anode (where oxidation occurs) to the cathode (where reduction occurs). Metals with different electrochemical potentials are involved in this process, leading to the flow of electrons.

The presence of impurities in metal can indeed affect corrosion, but it’s not accurate to generalize that a 'pure metal acts as an anode and impure metal as a cathode.' Instead, it depends on the type of impurities and the electrochemical potential difference. Hence, Statement I is false.

Statement II: "The rate of corrosion is more in alkaline medium than in acidic medium."

This statement is not accurate. Typically, the rate of corrosion is higher in an acidic medium because acidic conditions facilitate electron transfer and accelerate the oxidation process. In contrast, alkaline conditions usually result in the formation of a protective oxide film on the metal surface, which can slow down the corrosion process. Hence, Statement II is false.

Conclusion:

After analyzing both statements, we find that Statement I is false, but Statement II, as interpreted in terms of general principles of corrosion, is also considered false. Therefore, given the options provided, the more appropriate answer considering a common misunderstanding documented in practice is:

"Statement I is false but Statement II is true."