To prevent the corrosion of steel pipeline sections buried underground, engineers connect them to blocks of magnesium. This method of rust prevention is known as sacrificial protection.
Which statement correctly explains the chemical change that occurs to prevent the iron in the steel from rusting?
Magnesium is reduced to Mg2+Mg^{2+}Mg2+ ions because it is less reactive than iron, allowing the iron to remain in its elemental state.
Magnesium is oxidised to Mg2+Mg^{2+}Mg2+ ions because it has a greater tendency to lose electrons than iron, preventing the iron from oxidising.
Iron is oxidised to Fe2+Fe^{2+}Fe2+ ions preferentially, which then react with the magnesium to form a protective coating of magnesium oxide.
Iron is reduced to Fe3+Fe^{3+}Fe3+ ions by transferring electrons to the magnesium blocks, which halts the reaction with oxygen.
Practise Edexcel GCSE Chemistry Transition metals, alloys and corrosion with exam-style questions for Foundation and Higher tier. 97 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
