Preventing rusting by using sacrificial protection
3 marks · EasyIron pipes used in water supply networks are often fitted with zinc blocks to prevent rusting.
Describe what happens to the zinc block over time.
Explain how the zinc block prevents the iron pipe from rusting.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) The zinc block corrodes and becomes smaller/disappears over time.
(b) Zinc is more reactive than iron, so it reacts with oxygen and water instead of the iron. This prevents the iron from rusting.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States that the zinc block corrodes, is used up, or disappears with time.
M1 (b) · 1 mark · Mentions that zinc is more reactive than iron (or similar wording).
M2 (b) · 1 mark · States that zinc reacts (is oxidised) instead of iron, preventing rusting of the iron.
Worked solution
a) The zinc block slowly corrodes (oxidises) and gets used up over time.
b) Zinc is more reactive than iron, so it reacts with oxygen and water instead of the iron pipe. The zinc loses electrons and is oxidised, preventing the iron from losing electrons and rusting.