Preventing rusting by using sacrificial protection
3 marks · EasyThe table shows how the mass of a zinc sacrificial anode attached to an iron structure changes over four years.
| Year | Mass of zinc anode (g) |
|---|---|
| 0 | 500 |
| 1 | 425 |
| 2 | 355 |
| 3 | 295 |
| 4 | 240 |
State the decrease in mass of the zinc anode during the second year (from year 1 to year 2).
Explain why the zinc anode loses mass over time.
Describe how this process protects the iron structure 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) 70 g
(b) The zinc is oxidised/corrodes over time.
(c) Zinc reacts instead of iron, protecting iron from rusting.
Show mark scheme and worked solution
Marking points
A1 (a) · 1 mark · Correct calculation: 425 (year 1) - 355 (year 2) = 70 g.
M1 (b) · 1 mark · Explains that zinc is corroded or oxidised.
M2 (c) · 1 mark · States that zinc reacts (is oxidised) instead of iron, protecting the iron from rusting.
Worked solution
a) 425 - 355 = 70 g decrease during the second year.
b) The zinc loses mass because it is corroded/oxidised over time.
c) Zinc is more reactive than iron. It reacts (is oxidised) in place of iron, so the iron does not rust.