Preventing rusting by using sacrificial protection
2 marks · EasyAn iron water tank is protected from rust by a zinc block acting as a sacrificial anode. Over 24 months, the mass of the zinc block decreases from 800 g to 620 g.
Calculate the average mass of zinc lost per month. Show your working.
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Show answer
7.5 g (±0.1)
Common mistakes: 180; 0.27
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Subtracts the final mass from the starting mass to find total mass lost: 800 - 620 = 180 g.
A1 · 1 mark · Divides by 24 months to find mass lost per month: 180 / 24 = 7.5 g/month.
Worked solution
Total mass lost = 800 - 620 = 180 g
Average per month = 180 g / 24 months = 7.5 g/month