Methods of Extraction, Alloys, and Rusting

Question 1

How are Group 1 metals extracted?

Group 1 based on reactivity series

Answer 1

Group 1 metals are extracted by electrolysis because they are more reactive than carbon.

Question 2

How are Group 2 metals extracted?

Group 2 based on reactivity series

Answer 2

Group 2 metals are extracted by reduction with carbon because they are less reactive than carbon.

Question 3

How are Group 3 metals extracted?

Group 3 based on reactivity series

Answer 3

Group 3 metals are mostly found free in nature because they have very low reactivity and do not react with their surroundings.

Question 4

What are the raw materials needed for the extraction of aluminium?

Answer 4

1. Bauxite ore (Al₂O₃): Pure source of aluminium oxide.
2. Cryolite: Lowers the melting point of aluminium oxide.
3. Graphite (carbon): Used to make electrodes for electrolysis.

Question 5

What happens at the cathode during aluminium extraction?

Answer 5

At the cathode (-ve terminal), aluminium metal is produced.

• Half equation: Al³⁺ + 3e⁻ → Al.

Question 6

What happens at the anode during aluminium extraction?

Answer 6

At the anode (+ve terminal), oxygen gas (O₂) is produced.

• Half equation: 2O²⁻ → O₂ + 4e⁻
• The oxygen reacts with the carbon in the graphite electrode, forming CO₂: C + O₂ → CO₂.

Question 7

What are some uses of aluminium?

Answer 7

1. Body of aeroplanes: Low density.
2. Cooking pans: Good conductor of heat, non-toxic, resistant to corrosion.

Question 8

What are the raw materials needed for the extraction of iron?

Answer 8

1. Coke (carbon): Acts as a reducing agent and source of heat.
2. Haematite ore (Fe₂O₃): Main source of iron oxide.
3. Water: Acts as a cooling agent.
4. Hot air: For combustion.
5. Limestone (CaCO₃): Purifies iron from sand.

Question 9

How is iron extracted in a blast furnace?

Answer 9

Iron (II) oxide (FeO) is reduced by coke and carbon monoxide in the blast furnace to produce iron.

Question 10

How is steel made from iron?

Answer 10

1. Iron from the blast furnace is purified by blowing hot oxygen over it to remove impurities.
2. Carbon is added to form steel (an alloy).

Question 11

What are alloys?

Answer 11

Alloys are mixtures of a metal and one or more other elements (usually carbon). They have improved properties, such as increased hardness due to the distorted arrangement of atoms.

Question 12

What are the types of steel and their uses?

Answer 12

1. Low % carbon steel / Mild steel (0.25%): Easily shaped, used for car bodies.
2. High % carbon steel (2.5%): Harder, used for cutting tools.
3. Stainless steel (Fe/Cr/Ni): Resistant to corrosion, used for cutlery and sinks. Expensive.

Question 13

What are the uses of iron?

Answer 13

1. Railway tracks: High strength.
2. Car bodies: Strong, malleable.

Question 14

What are the uses of copper?

Answer 14

1. Electric wiring: Ductile and good conductor of electricity.
2. Sauce pans: Malleable, good conductor of heat, unreactive.

Question 15

How does iron rust?

Answer 15

Iron rusts in the presence of water and oxygen, forming iron (III) oxide.

Question 16

What are barrier methods for preventing rusting?

Answer 16

1. Painting: Used for steel bridges and railings.
2. Oiling/Greasing: Used for tools, machine parts, and bicycle chains.

These methods prevent water and oxygen from reaching the iron. If scratched, they no longer prevent rust.

Question 17

What is the sacrificial method for preventing rusting?

Answer 17

Galvanizing: Iron is coated with zinc. Zinc acts as a barrier and is more reactive than iron. When scratched, zinc oxidizes instead of the iron, protecting it.

• Zinc equation: Zn → Zn²⁺ + 2e⁻
• Iron equation: Fe → Fe²⁺ + 2e⁻