Home / iGCSE Chemistry Multiple Choice (Extended) : 9.5 Corrosion of metals: Exam Style Questions Paper 2

iGCSE Chemistry Multiple Choice (Extended) : 9.5 Corrosion of metals: Exam Style Questions Paper 2

iGCSE Chemistry MCQ (Extended) Paper 2 - All Chapters
Question

Part of a steel ship is protected from rusting using a sacrificial metal.

What is a suitable sacrificial metal?

A) copper
B) zinc
C) silver
D) potassium

▶️ Answer/Explanation
Solution

Ans: B

Sacrificial protection requires a metal that is more reactive than iron (in steel):

1. Copper (less reactive than iron) would actually accelerate rusting

2. Zinc is more reactive than iron and commonly used for this purpose (galvanization)

3. Silver is less reactive than iron

4. While potassium is more reactive, it’s too reactive (reacts violently with water) for practical use

Zinc is the standard choice as it’s sufficiently reactive to protect iron but stable enough for practical applications.

Question

Which statements about the use of sacrificial protection to prevent iron from rusting are correct?

  1. A more reactive metal than iron is used as a sacrificial protector because it undergoes reduction before iron.
  2. Zinc is used as a sacrificial protector because it gains electrons more readily than iron.
  3. Copper is not used as a sacrificial protector because it is less reactive than iron.
  4. Magnesium is used as a sacrificial protector because it loses electrons more readily than iron.

A) 1 and 2
B) 1 and 4
C) 2 and 3
D) 3 and 4

▶️ Answer/Explanation
Solution

Ans: D

Statement 1 is incorrect because the sacrificial metal undergoes oxidation (loses electrons), not reduction. Statement 2 is wrong because zinc loses electrons more readily, not gains them. Statement 3 is correct – copper is less reactive than iron and wouldn’t protect it. Statement 4 is correct – magnesium is more reactive and loses electrons more readily than iron, making it an excellent sacrificial protector. Therefore, the correct combination is 3 and 4 (option D).

Question

 Mild steel is galvanized to prevent corrosion of the iron.

Which statements about galvanizing are correct?

  1. Galvanizing prevents corrosion because the zinc forms an alloy.
  2. If the coating is damaged, water and oxygen do not corrode the iron.
  3. Zinc is a sacrificial metal and corrodes in preference to iron.

A 1 and 2                B 1 and 3                 C 2 only                D 2 and 3

Answer/Explanation

Ans:

D

Question

Covering iron with zinc prevents the iron from rusting even when the zinc is scratched. Covering iron with tin prevents the iron from rusting, but when the tin is scratched the iron underneath starts to rust.
Which statement is correct?
A Both tin and zinc prevent iron from rusting by sacrificial protection.
B Both tin and zinc prevent iron from rusting by stopping water and carbon dioxide reaching the
iron.
C Tin is more reactive than iron and prevents iron from rusting until it is scratched.
D Zinc loses electrons more easily than iron and prevents iron from rusting by corroding first.

Answer/Explanation

Ans: D

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