Chemistry 9th Chap 7 : Topic 10 - Maryam Publications

Chemistry Chapter 7 : Topic 10

Corrosion Prevention

1 / 20

Which statement best defines corrosion in metals?

A) It is the slow chemical deterioration of metals due to reaction with environmental elements like oxygen, water, or acids

B) It is the melting of metals at high temperature

C) It is the physical breaking of metals into smaller pieces due to force

D) It is the process of mixing metals to form alloys

2 / 20

A student observes rust formation on an iron gate exposed to rain and air for a long time. Which conclusion is most accurate?

A) Rusting occurs due to oxidation of iron in presence of oxygen and moisture

B) Rusting is caused by cooling of iron surface

C) Rusting is a physical change caused by weathering

D) Rusting happens due to evaporation of iron particles

3 / 20

Which condition is MOST essential for rusting of iron to occur?

A) Presence of water only

B) Presence of carbon dioxide only

C) Presence of both oxygen and moisture

D) Presence of oxygen only

4 / 20

Painting iron structures is considered an effective method of corrosion prevention because:

A) It cools the metal surface

B) It changes iron into a non-metal

C) It increases the weight of iron

D) It acts as a barrier preventing contact with air and moisture

5 / 20

Which method of corrosion prevention involves coating iron with a layer of zinc?

A) Electroplating

B) Sacrificial protection

C) Alloy formation

D) Galvanization

6 / 20

Why does zinc coating protect iron even if scratched?

A) Zinc prevents all physical damage

B) Zinc turns into iron oxide

C) Zinc is softer than iron

D) Zinc reacts faster than iron and protects it sacrificially

7 / 20

Electroplating is used to prevent corrosion by:

A) Removing impurities by filtration

B) Mixing two metals together permanently

C) Covering metal with a thin layer of another metal using electric current

D) Heating the metal to high temperature

8 / 20

Which of the following is an example of sacrificial protection in ships?

A) Painting the ship only

B) Attaching magnesium blocks to the ship’s hull

C) Heating the ship surface

D) Using plastic coating

9 / 20

Why are magnesium or zinc blocks attached to underground pipelines?

A) To act as sacrificial metals that corrode instead of iron

B) To increase pipeline strength

C) To make pipelines heavier

D) To increase electrical conductivity

10 / 20

Which statement correctly distinguishes galvanization from electroplating?

A) Both use zinc only

B) Galvanization uses zinc, while electroplating can use different metals like chromium or nickel

C) Galvanization uses electric current always

D) Electroplating is a natural process

11 / 20

A newly painted iron bridge still begins to rust after some time due to scratches. What is the BEST explanation?

A) Iron converts into paint

B) Oxygen reacts with paint

C) Exposed iron areas allow air and moisture to reach metal surface

D) Paint increases rusting rate

12 / 20

Why is corrosion considered economically harmful?

A) It leads to loss of metal structures and increases maintenance cost

B) It makes metals stronger

C) It improves metal durability

D) It increases production of metals

13 / 20

Which of the following metals is commonly used for electroplating to improve appearance and prevent corrosion of utensils?

A) Hydrogen

B) Sodium

C) Potassium

D) Chromium

14 / 20

Barrier methods of corrosion prevention work mainly by:

A) Increasing rust formation

B) Heating metal surface

C) Changing metal into another substance

D) Slowing down chemical reactions by separating metal from environment

15 / 20

Which of the following is NOT a barrier method of corrosion prevention?

A) Galvanization

B) Painting

C) Plastic coating

D) Oiling/greasing

16 / 20

Oil or grease is used to protect machine parts from corrosion because it:

A) Converts iron into alloy

B) Forms a protective layer that prevents contact with air and moisture

C) Increases rust formation

D) Reacts chemically with iron

17 / 20

Which of the following situations will increase corrosion rate most?

A) Vacuum environment

B) Dry environment with no oxygen

C) Humid and salty coastal environment

D) Cold and dry climate

18 / 20

Sacrificial protection works because:

A) Metals become non-reactive permanently

B) More reactive metals corrode in place of less reactive metals

C) Less reactive metals protect more reactive metals

D) Metals stop reacting completely

19 / 20

Why is tin sometimes used for coating food cans instead of zinc?

A) Tin is less reactive and does not react with food easily.

B) Tin is more reactive than iron.

C) Tin dissolves in water easily.

D) Tin corrodes faster than iron.

20 / 20

Which combination correctly represents methods of corrosion prevention?

A) Crushing, grinding, hammering

B) Melting, boiling, evaporating

C) Painting, galvanizing, electroplating, sacrificial protection

D) Heating, freezing, cutting

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