Question

In electrochemical corrosion of metals, the metal undergoing corrosion : (a) acts as anode (b) acts as cathode (c) undergoes reduction (d) None

Short answer

In electrochemical corrosion of metals, the metal undergoing corrosion acts as an anode.

Step-by-step solution

Identify the Process of Corrosion

Corrosion is an electrochemical process involving the transfer of electrons. The metal being corroded loses electrons in this process.

Determine the Role of the Metal in Corrosion

In an electrochemical cell, the site where oxidation occurs and electrons are lost is the anode. Therefore, during corrosion, the metal acts as the anode.

Distinguish Between Anode and Cathode in Oxidation-Reduction

The anode is where oxidation takes place, which is the loss of electrons. The cathode is where reduction takes place, which is the gain of electrons. Since the metal loses electrons, it does not act as the cathode and does not undergo reduction.

Conclusion

Based on the process of electrochemical corrosion where the metal loses electrons, the correct answer is that the metal acts as an anode.

Key concepts

Anode and Cathode in Electrochemistry

Understanding the terms anode and cathode is essential in the study of electrochemistry. In an electrochemical cell, these are the terminals where crucial reactions occur. The anode is the site where oxidation takes place - that's where a substance loses electrons.

On the other hand, the cathode is the stage for reduction, a process in which a substance gains electrons. This electron game is akin to a dance where anode 'gives out' electrons as if it's giving away dance invitations, and cathode 'accepts' electrons as if it's accepting those invitations to start dancing.

In the case of corrosion, the metal under attack gives away electrons and, hence, dances the role of an anode. It's important to remember that anode and cathode are not fixed labels; they are based on the direction of the electron flow, which can change depending on the type of reaction.

Oxidation-Reduction (Redox) Reactions

Any student delving into chemistry needs to grasp the concept of oxidation-reduction, or redox, reactions. They are the processes that underpin a range of phenomena, from combustion to metabolism, and of course, corrosion. Redox reactions involve the transfer of electrons between substances.

Oxidation refers to the loss of electrons, while reduction speaks to the gain of them. These two halves of a redox reaction are inseparable - if something is oxidized, something else must be reduced. Picture them like a seesaw; for one side to go up (oxidation), the other side must come down (reduction).

These reactions can be easily remembered by the mnemonic 'LEO says GER': Lose Electrons Oxidation, Gain Electrons Reduction. When metal corrodes, it is undergoing oxidation; it is losing electrons, much like a tree loses its leaves in autumn.

Corrosion Process

The corrosion of metals can be seen as their gradual destruction through a spontaneous redox reaction with environmental elements such as oxygen or water. This is not just a superficial change; corrosion affects the entire bulk of the metal over time.

In this process, metals act as the anode and lose electrons, thereby getting oxidized. It's akin to a slow burn, with the metal giving up pieces of itself in the form of electrons. This electron-loss can weaken metals and lead to structural failures, a significant concern in infrastructures like bridges or buildings.

Environmental factors accelerate corrosion; for example, saltwater can spur the activity, eating away at the metal at a much faster pace. This is why vehicles in coastal areas often suffer more from rust, which is the common term for the corrosion of iron.

Electron Transfer in Chemistry

Electrons are the currency of chemical reactions. Electron transfer is the mechanism behind many chemical changes, including the redox reactions central to corrosion. When a metal corrodes, it loses electrons - technically, it 'oxidizes' - and in doing so, it undergoes a fundamental transformation.

This loss of electrons may be due to reaction with substances like oxygen or acids. The electron transfer is not a solo act; the departed electrons must go somewhere. They often end up with a non-metallic element or compound gaining these electrons, meaning it's reduced.

This transfer isn't visible to the naked eye, but its effects are. The once strong metal is now weakened, pitted, or crumbly, all because of the unseen flow of electrons. This microscopic process has macroscopic consequences, such as the need for costly repairs or replacements due to corroded materials.