(a) Magnesium metal is used as a sacrificial anode to protect underground pipes from corrosion. Why is the magnesium referred to as a “sacrificial anode”? (b) Looking in Appendix E, suggest what metal the underground pipes could be made from in order for magnesium to be successful as a sacrificial anode.

Verified step by step guidance

1. Step 1: Understand the concept of a sacrificial anode. A sacrificial anode is a metal that is more reactive (more easily oxidized) than the metal it is protecting. It corrodes instead of the protected metal, hence the term 'sacrificial'.
2. Step 2: Identify the role of magnesium in this context. Magnesium is used as a sacrificial anode because it has a higher tendency to oxidize compared to many other metals, meaning it will corrode first, protecting the other metal from corrosion.
3. Step 3: Refer to Appendix E or a standard electrode potential table to find the standard reduction potentials of various metals. The metal with a more positive standard reduction potential than magnesium will be protected by magnesium.
4. Step 4: Compare the standard reduction potential of magnesium with other metals. Magnesium has a standard reduction potential of -2.37 V. Look for metals with a more positive standard reduction potential.
5. Step 5: Suggest a suitable metal for the underground pipes. Based on the comparison, choose a metal like iron (Fe), which has a standard reduction potential of -0.44 V, making it suitable to be protected by magnesium as a sacrificial anode.