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Chemistry > Metal Extraction > Flashcards

Metal Extraction Flashcards

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0
Q

What is the most important factor to consider when extracting metals

A

Cost

The raw materials must be as cheap as possible
Process must be cost efficient
Metal must be profitable to manufacture

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1
Q

What is an ore

A

A rock that contains enough metal to make extraction feasible

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2
Q

Very few metals are found……

A

Native ( uncombined with nature)

They must be mined, extracted from their ores before use

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3
Q

Iron is mainly extracted from which ore

A

Haematite

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4
Q

What is haematite

A

The main ore for extraction iron

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5
Q

What process extracts iron from haematite

A

Smelting in the blast furnace

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6
Q

What does smelting use

A

Relatively cheap raw materials

Eg iron ore, coke ( cheap form of carbon), air and limestone

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7
Q

What happens when iron is smelted

A

The iron ore is heated with coke in a blast of hot air, converts coke to carbon monoxide. This reduces the iron ore to iron. The limestone is added to remove the silicon dioxide impurities to form calcium silicate

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8
Q

What other metals can be extracted in a similar way to iron

A

Manganese and copper

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9
Q

Why can’t aluminium be extracted through smelting

A

T is too reactive to extract using reduction by carbon

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10
Q

What is the most common ore in aluminium

A

Bauxite (40-60% of aluminium oxide)

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11
Q

Bauxite is purified to ……

A

Pure alumina at the mine to save transportation costs

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12
Q

Why is bauxite purified to alumina at the mine

A

To save transportation costs

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13
Q

What is the alumina mixed with

A

Molten cryolite

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14
Q

What does the molten cryolite do to the alumina

A

Reduces the temp need to melt the pure alumina

Saves money on energy costs

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15
Q

What is the advantage of adding molten cryolite to the alumina

A

It reduces the temp needed to melt the pure alumina so saves money on energy costs

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16
Q

What happens to the molten alumina and cryolite mixture

A

Undergoes electrolysis to make pure aluminium at the carbon cathode

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17
Q

Where is the pure aluminium formed

A

At the carbon cathode

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18
Q

What mixture undergoes electrolysis in the extraction of aluminium

A

The molten alumina and cryolite mixture

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19
Q

In aluminium extraction, the released oxygen reacts with the anode to form

A

CO2

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20
Q

What is the major cost process in the extraction of aluminium

A

The anodes wear out fast so have to be replaced each month

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21
Q

How is aluminium removed from the reactor

A

By siphoning (sucking) the liquid into huge crucibles. Theses are emptied into molds and are cast

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22
Q

Why is titanium an important and valuable metal

A

Due to its hardness, high melting point and strength. It’s lighter and stronger than steel, does not corrode

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23
Q

What is the main ore in titanium

A

Rutile, Mainly formed of titanium oxide

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24
Q

Rutile, the main ore in titanium is mainly formed of

A

Titanium oxide

25
Q

Why can’t titanium be obtained by coke reduction

A

Because titanium carbide is formed , makes it very brittle

26
Q

How is titanium removed

A

Titanium oxide heated with carbon in stream of chlorine gas. Converts titanium to titanium chloride, which is a gas at the operating temp. The titanium chloride is purified by fractional distillation under inert gas atmosphere. chloride is reduced in furnace by with a reactive metal eg magnesium or sodium. This has to be done in an inert atmosphere of argon as the sodium or magnesium would react with oxygen

27
Q

What conditions must the displacement of the chlorine for a more reactive metal take place in, in extraction of titanium

A

Inert gas atmosphere of argon

28
Q

What is an inert gas atmosphere

A

A non reactive gas atmosphere eg argon

29
Q

How are the impurities removed in titanium extraction

A

Gentle heating

30
Q

Disadvantages of titanium extraction

A

Batch process, not continuous like aluminium and iron extraction, therefore production is slower and more expensive. Also expensive as magnesium is expensive, this makes titanium expensive and it has not yet displaced steel despite its superior properties (stronger,lighter etc)

31
Q

Uses for titanium

A

Used for high value uses such as jet turbine blades, hip joints where it’s cost is outweighed by its superior performance

32
Q

What is tungsten and what is its uses

A

Very strong with high melting point
Added to steel to make it very hard.
Major use is in bulb filaments

33
Q

Can tungsten be extracted by reduction using carbon? Why?

A

No as tungsten carbide is formed. This is hard and brittle and used to make machinery parts and tools

34
Q

Main ore in tungsten

A

Tungsten oxide

35
Q

How is tungsten separated from its ores

A

The ores are crushed and the tungsten compounds are separated by gravity/magnetic methods. Converted into tungsten oxide. This is reduced by heating with hydrogen

36
Q

Tungsten is extracted using….

A

Hydrogen

37
Q

Tungsten can be extracted from its oxide with carbon but….

A

Can leave impurities (tungsten carbide) which make the metal brittle

38
Q

Which is the only metal reduced on a large scale using hydrogen

A

Tungsten

39
Q

What is the issue with using hydrogen to reduce tungsten

A

It is expensive, but it’s worth the extra cost to get pure tungsten which is easier to work with

40
Q

Hazard of using hydrogen to reduce tungsten

A

Highly explosive when mixed with air

41
Q

Metals are often found on ores as….

A

Sulphides (lead and zinc sulphide)

42
Q

What is the first step to extract a metal from a sulphide ore

A

Turn it into an oxide. This is done by roasting the sulphide in air

43
Q

What happens when you roast the sulphide in air

A

This is the first step to extract a metal from a sulphide ore.

44
Q

After the sulphide ore is roasted, what is produced

A

An oxide and sulphur dioxide

45
Q

What is the issue with forming sulphur dioxide in the process of turning an sulphide ore into an oxide

A

Sulphur dioxide causes acid rain, which can’t be released into the atmosphere

46
Q

What is done to the sulphur dioxide which is produced during the first step of extracting a metal

A

Converted into sulphuric acid, which is useful as it is in big demand as it’s used in many chemical and manufacturing processes

47
Q

What happens after the metal oxides have been reduced

A

Depends on the metal that is being extracted

Coke and carbon monoxide used as reducing agents in many metals

48
Q

3 examples of the extraction of metals with carbon or carbon monoxide

A

Reduction of..

Iron oxide

Manganese oxide

Copper carbonate

49
Q

Main ore in copper

A

Malachite

50
Q

2 methods of extracting copper from its ore

A

Carbon (coke)
And
Heating the carbonate until it decomposes, then reducing the oxide with carbon

51
Q

Why are carbon and carbon monoxide the first choice for extracting metals

A

Cheap

52
Q

Aluminium is extracted from its ore by….

A

Electrolysis

53
Q

Why is it too expensive to reduce aluminium from its ore

A

Needs a very high temp

54
Q

Why isn’t titanium used more

A

It’s difficult and expensive to produce

55
Q

Why is an inert gas atmosphere used

A

To prevent side reactions

56
Q

Advantages of recycling metals

A

Saves raw materials ores are finite resources

Saves energy - recycling metals takes less energy than extracting metal so saves money

Reduces waste sent to landfill

Mining damages the landscape, recycling reduces this

57
Q

Disadvantages of recycling metals

A

Collecting and sorting metals from other waste can be difficult and expensive

The purity of the recycled metal varies - usually other metals and other impurities mixed in

Recycling metals may not produce a consistent supply to meet demand

58
Q

Scrap iron can be used in…..

A

Copper extraction

This method mainly used with low grade ore (ore that contains a small percentage of copper)

59
Q

How is scrap iron used in copper extraction

A

Acidified water dissolves the copper compounds in the ore. The solution is collected and scrap iron added. The iron dissolves and reduces the copper ions. The copper precipitates out of the solution.

60
Q

Advantages of using scrap iron to extract copper

A

It’s cheaper than carbon reduction as you don’t need high temps and better for environment as no CO2 produced

61
Q

Disadvantages of using scrap iron to extract copper

A

This process produces copper more slowly than carbon reduction and has a lower yield which is why it’s not used with ores that have a high copper content.

Chemistry (17 decks)

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