9.6 Extraction of metals

How easy is it to extract unreactive metals

They are found in their pure form due to low reactivity. They are easier to extract.

How are zinc and iron in ores

They are found as oxides(zinc oxide, iron oxide)

How are zinc and iron extracted

They are extracted by reduction with carbon.

Carbon is more reactive, therefore it displaces the metal in the compound, leaving pure metal

What is reduction?

A chemical process where a substance gains electrons or loses oxygen atoms

How are highly reactive metals extracted

By electrolysis. They are harder to extract because they react strongly with other elements.

What is the iron ore called?

Hematite

How is iron extracted?

Using a blast furnace

What is added to the top of the furnace?

Iron ore and other materials are added at the top while hot air is blasted from the bottom

What is the first stage of extraction of iron?

• Burning of Carbon(coke)

It releases heat needed for the process

The burning produced co2

Carbon+oxygen→carbon dioxide

What is the second stage of extraction of iron?

• Reduction of co2

The co2 reacts with more coke in the furnace to produce carbon monoxide, through reduction

C+CO2→2CO

What is the 3rd stage of extraction of iron?

• Reduction of Iron(III)oxide

Carbon monoxide gas react with iron(III)oxide(from hematite)to produce molten iron and co2

Fe2O3+3CO→2Fe+3CO2

What is the fourth stage of iron extraction

Thermal decomposition of calcium carbonate:

• Calcium carbonate(limestone)is added to the furnace

• It decomposes under high heat to produce calcium oxide and carbon dioxide

• The calcium oxide helps to remove impurities from iron ore

CaCO3→CaO+CO2

What is the last stage of extraction of iron?

Formation of Slag:

• Calcium oxide reacts with impurities in the iron ore to form a slag

• The slag floats on top of molten iron and can be removed

Calcium oxide+silicon dioxide→calcium silicate

CaO+SiO2→CaSiO3

What are the stages of extraction of iron?

• Burning of carbon(coke)

• Converting carbon dioxide to carbon monoxide

• Using carbon monoxide to reduce iron(III)oxide to iron

• Thermal decomposition of calcium carbonate to produce calcium oxide to remove impurities

• Form of slag to separate impurities from molten iron

What are the symbol reactions for extraction of iron from hematite

• C+O2→CO2

• C+CO2→2CO

• Fe2O3+3CO→2Fe+3CO2

• CaCO3→CaO+CO2

• CaO+SiO2→CaSiO3

What is the main ore of aluminium

Bauxite

How is aluminium extracted from bauxite?

Through electrolysis

What is the role of cryolite in extraction of aluminium

• reduces melting point of aluminium oxide

• Increases conductivity of electrolyte

• Makes process more efficient

Explain electrolysis process of aluminium

• Aluminium ions move to cathode where they gain electrons and form pure aluminium

• Oxygen ions move to anode and form oxygen gas

What happens at the anode?

Anions lose electrons(oxidation)

2O(2-)→O2+4e-

What happens at the cathode?

Cations gain electrons(reduction)

Al(3+)+3e—>Al

OIL RIG

Oxidation is Loss of electrons

Reduction is Gain of electrons

Why do carbon anodes need to be regularly replaced?

• The carbon in graphite anodes react with oxygen produced to form co2

• This reaction causes the anode to wear out over time