Topic 4 - IRON RUSTING Flashcards
What is rust?
Chemical reaction between IRON, WATER AND OXYGEN to form IRON(III) OXIDE
The corrosion of iron
What are the conditions under which iron rusts?
- O2 and water must be present for rust to occur
- presence of SODIUM CHLORIDE increases speed of rusting
What is the word equation for iron rusting?
iron + water + oxygen —> Hydrated iron (III) oxide
How can the rusting of iron be prevented?
using:
- barrier methods
- galvanising
- sacrificial protection
What are barrier methods?
Rust can be prevented by coating iron with barriers that PREVENT iron coming in contact with water + O2.
What happens if the coating barriers in barrier method are washed away/scratched?
Iron again exposed to WATER + OXYGEN (will rust)
Name some common barrier methods
GREASE > OIL
PAINT > PLASTIC
What is Galvanising?
Galvanising: when iron is coated with layer of ZINC.
(ZnCO3 formed when xinc reacts with O2 in air) -> this protects iron by barrier method.
What happens if coating in galvanising method is damaged/scratched?
Iron is still protected from rusting by sacrificial method.
Mg can also be used
Why is Zinc used to prevent iron from rusting?
Zinc is MORE REACTIVE than iron so it reacts with water + oxygen and corrodes instead of iron.
What is oxidation?
Loss of electrons + gain of O2 (increase in oxidation state)
What is reduction?
Gain of electrons + loss of O2 (decrease in oxidation state).
What is REDOX?
Reaction where oxidation + reduction occur together.
What is an oxidising agent?
Substance that gains electrons + looses oxygen, OXIDISES OTHERS BUT REDUCES ITSELF
What is a reducing agent?
Substance that loses electrons + gains oxygen REDUCES OTHERS BUT OXIDISES ITSELF
