Chapter 22, Problem 4STP

Interpretation Introduction

Interpretation:

The sacrificial anodes need to be explained.

Concept introduction:

The rusting of iron takes place when oxidation of iron takes place which results in the formation of iron oxide when iron comes in contact with moisture in air.

Answer to Problem 4STP

Correct Answer: Option (d)

Explanation of Solution

Reason for correct option: If sacrificial anodes are attached to rust susceptible iron to prevent corrosion thus, the sacrificial anodes must oxidize more than iron.

In oxidation reaction, loss of electrons takes place thus; the sacrificial anodes must lose electrons more easily than iron.

Therefore, option (d) is correct.

Conclusion

Reason for incorrect option: If the sacrificial anodes are more likely to be reduced than iron thus, it will undergo reduction and the oxidation of iron takes place. Thus, sacrificial anode will not prevent corrosion of iron.

If sacrificial anodes have higher reduction potential, it will undergo reduction and again it cannot prevent corrosion of iron.

If sacrificial anodes are more porous than iron they cannot get easily oxidized as oxide layer cannot be formed easily on porous surface. Thus, it cannot prevent corrosion of iron.

Therefore, options (a), (b) and (c) are incorrect.