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CAIE IGCSE Chemistry Reactivity and Electron Loss in Sacrificial Protection

CAIE IGCSE Chemistry Reactivity and Electron Loss in Sacrificial Protection
Cambridge IGCSE Chemistry 0620 syllabus for exams in 2026, 2027 and 20282026–2028

Practise explaining sacrificial protection with a metal above iron in the reactivity series that loses electrons and corrodes preferentially.

How this is tested

  • select magnesium or zinc because it is more reactive than iron and oxidises first
  • state that the sacrificial metal loses electrons more readily than the protected iron
  • reject copper or another metal below iron because it cannot provide sacrificial protection

Question 6

[Maximum number: 3]

This question is about iron.

Question 6(c)

(a)

Steel consists mainly of iron.

Iron rusts when it reacts with water and oxygen.
Fig. 6.2 shows magnesium blocks attached to the bottom of a steel boat. The magnesium does not completely cover the steel.

The magnesium blocks provide sacrificial protection for the steel.

Fig. 6.2

Fig. 6.2

[ 3 ]

Question 6(c)(i)

(i)

Explain, in terms of electrons, why magnesium is used for sacrificial protection.

[ 2 ]

Question 6(c)(ii)

(ii)

Name a metal that cannot provide sacrificial protection for steel.

[ 1 ]