Preventing rusting by using sacrificial protection
2 marks · HardExplain why a block of copper cannot be used as a sacrificial anode to protect iron from rusting.
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Also accept: Copper is less reactive than iron, so it will not corrode (oxidise) in preference to iron and cannot act as a sacrificial anode.; Copper is less reactive than iron; it will not lose electrons in preference to iron and will not prevent rusting of the iron.
Common mistakes: Stating that copper will protect because it is a metal or because it covers the iron.; Focusing only on physical covering rather than reactivity.
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Marking points
M1 · 1 mark · States that sacrificial anode must be more reactive than iron or that copper is less reactive than iron.
A1 · 1 mark · Explains that since copper is less reactive, it will not oxidise (corrode) instead of iron; therefore, it cannot protect iron.
Worked solution
Copper cannot be used as a sacrificial anode because it is less reactive than iron. It will not corrode or oxidise in preference to the iron, so it does not provide sacrificial protection.