In marine engineering, sacrificial anodes are commonly attached to the steel hulls of ships to prevent the corrosion of iron in seawater.
Which metal is suitable for use as a sacrificial anode, and what is the correct explanation for its protective action?
Copper, because it is less reactive than iron and will prevent the iron from losing electrons by acting as an electron sink.
Zinc, because it is more reactive than iron and will be preferentially oxidised, supplying electrons to the iron hull.
Tin, because it is more reactive than iron and will undergo sacrificial oxidation to form a self-healing barrier of tin(II) oxide.
Silver, because it is highly unreactive and will transfer electrons to iron ions to reduce them back to metallic iron.
97 exam-style questions on Edexcel GCSE Chemistry 6.1 Transition metals, alloys and corrosion, covering 6.1.1 Properties of transition metals, 6.1.2 Corrosion and its prevention, and 6.1.3 Alloys and the uses of metals. Each one has a worked solution and a mark scheme showing where the marks go.