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Chemistry > Unit 13 > Flashcards

Unit 13 Flashcards

1
Q

Metal ores

Sodium =

A

Rock salt

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2
Q

Metal ores

Aluminium =

A

Bauxite

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3
Q

Metal ores

A

Iron = hematite

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4
Q

Method of extraction

A

Potassium, k. Most reactive
Sodium, na Ores more difficult to
Calcium, ca Decompose
Magnesium, mg More expensive
Aluminium , al More difficult
———————————————
Carbon
———————————————
Zinc, zn Heating with a reducing agent
Iron, fe (Carbon or carbon monoxide)
Lead, pb
———————————————
Hydrogen
———————————————
Copper, cu Occur naturally as elements
Silver, ag So no chemical reaction is needed
Gold, au Only separation from impurities

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5
Q

Extraction of zinc from zinc blend

A

Zinc is mainly zinc sulphide, ZnS. First it is roasted in air, giving zinc oxide

Zinc sulphide + oxygen –> zinc oxide + sulphur dioxide
2ZnS + 3O –> 2ZnO + 2SO2
Then the oxide is reduced in one of the two ways below:
1. Using carbon monoxide. This is carried in a furnace:
Zinc oxide + carbon monoxide –> zinc + carbon dioxide
ZnO + CO –> Zn + CO2
The final mixture contains zinc and a slag of impurities. The zinc is separated from it by fractional distillation

  1. Electrolysis
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6
Q

Extraction of iron

A

A mixture called the charge, containing the iron ore, is added through the top of the furnace. Hot air is blasted in through the bottom. After a series of reactions, liquid iron collects at the bottom of the furnace

The charge contains three things

  1. Iron ore.
  2. Limestone
  3. Coke
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7
Q

The reactions in a blast furnace

Stage 1: the coke burns giving off heat

A

The blast of hot air starts the coke burning. It reacts with the oxygen in the air, giving carbon dioxide:

Carbon + oxygen–> carbon dioxide
C + 02 = CO2

It’s a combustion reaction which means it’s a redox reaction. The carbon is oxidised to carbon dioxide. The blast of air provides the oxygen for the reaction.

The reaction is exothermic - it gives off heat , which helps to heat the furnace

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8
Q

The reactions In the blast furnace

Stage 2: carbon monoxide is made

A

The carbon dioxide reacts with more coke, giving carbon monoxide:

Carbon + carbon monoxide –> carbon monoxide
C + CO2 = 2CO

In this redox reaction, the carbon loses oxygen. It is reduced
The reaction is endothermic- it takes in heat from the furnace. This is good because stage 3 needs a lower temperature

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9
Q

The reaction in the blast furnace

Stage 3: the iron (111) oxide is reduced

A

This is where the actual extraction occurs. Carbon monoxide reacts with the iron ore giving liquid iron
Iron + carbon monoxide –> iron + carbon dioxide
Fe2O3 + 3CO –> 2Fe + 3CO2
The iron trickles to the bottom of the furnace
In this redox reaction, carbon monoxide acts as the reducing agent. It reduces the iron (111) oxide to the metal
At the same time the carbon monoxide is oxidised to carbon dioxide

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10
Q

What is limestone used for?

A

The limestone reacts with the sand (silica) in the ore, to form calcium silicate or slag

Limestone + silica –> calcium silicate + carbon dioxide
CaCO3 + SiO2,–> CaSiO3 + CO2

The slag runs down the furnace and floats on the iron
The purpose of this reaction is to remove impurities from the molten iron
Silica is an acidic oxide . It’s reaction with limestone is neutralisation (because limestone is a base) giving calcium silicate , a salt

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11
Q

Waste gases

A

Carbon dioxide and nitrogen. They come out the top of the furnace

The carbon dioxide is from the reduction in stage 3. The nitrogen is from the air blast. It has taken part in the reactions so has not been changed

The molten iron is tapped from the bottom. It is impure with carbon as the main impurity . Some is run into moulds to give cast iron this is hard but brittle. But most of the iron is turned into steel

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12
Q

Use of aluminium and what properties make it useful

A

Overhead electricity cables (w steel core for strenghth) , coating DVDs and cds, cooking foil and food cartons , drink cans

Good conductor of electricity, ductile , resists erosion, non toxic, shiny service that reflects the laser beams that reads cds and dvds, can be rolled into thin sheets

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13
Q

Uses for copper and what properties make it useful

A

Electrical wiring , roofing , saucepan bases

One of the best conductors of electricity, ductile , malleable , develops an attractive protective coating conducts heat well , unreactive , tough

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14
Q

Uses for lead and what properties make it useful

A

Holding the glass in stained glass windows, and sealing joins in roofs car batteries

Easy to bend at room temp , unreactive
Gives a current when connected to lead oxide in an electrolyte (dilute sulphuric acid)

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15
Q

Uses of zinc and what properties make it useful

A

Protecting steel from rusting coating or galvanising iron and steel for torch batteries

Offers sacrificial protection if coating cracks gives a current when connected to a carbon electrode, in an electrolyte

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16
Q

Uses of silver and what properties make it useful

A

Electrical connections inside mobile phones, keyboards, and photovoltaic (PV) cells mirrors , and mirrored sunglasses jewellery

The best metal of all at conducting electricity, ductile.
Reflects light very well, even in a very thin coat looks good, and resists corrosion

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17
Q

Uses of titanium and what properties make it useful

A

Tooth implants, and replacement hip and knee joints. Exhaust pipes for planes pipes and tanks in chemical factories

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18
Q

What is an alloy

A

A mixture of metals that changes there properties or increase them. Turing a metal into an alloy increases its range of uses

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19
Q

How to make mild steel

A

When Carbon (0.5%) is mixed with pure iron the result is mild steel

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20
Q

What are the uses of mild steel

A

Building, ships , car bodies and machinery

21
Q

How to make stainless steel

A

When nickel and chromium are mixed with iron, the result is stainless steel. This Is hard and rustproof

22
Q

Uses of stainless steel

A

Car parts, kitchen sinks and cutlery

23
Q

Atoms in a pure metal

A

They are arranged in a regular lattice. (In fact they are metal ions) in a sea of electrons)

24
Q

When pressure is applied to a metal, for example by hammering the metal

A

The layers can slide over each other easily. That is why a metal is malleable and ductile

25
Q

Structure when the metal turns to an alloy

A

New atoms enter the lattice. The layers can no longer slide easily. So the alloy is stronger than the original metal

26
Q

The first stage of making steels

A

Unwanted impurities are removed from the iron

The molten iron from the blast furnace is poured into an oxygen furnace. Calcium oxide is added, and a jet of oxygen is turned on. The calcium oxide neutralises any acidic impurities, forming a slag that is skimmed off. The oxygen reacts with the other burning them away

27
Q

The second stage of making steels

A

Then other elements may be added

This is measured out carefully, to give steels with the required properties

28
Q

What is the alloy stainless steel made up of

A

70% iron
20% chromium
10% nickel

29
Q

Special properties of a stainless steel

A

Does not rust

30
Q

Uses of stainless steel

A

Car parts, kitchen sinks, cutlery, tanks and pipes in chemical factories, surgical instruments

31
Q

What is aluminium (alloy number 7075 TF) made from

A

90.25% aluminium
6% zinc
2.5% magnesium
1.25% copper

32
Q

What are the properties of aluminium (alloy number 7975 TF)

A

Light but very strong

33
Q

Uses of aluminium (7075 TF)

A

Aircraft

34
Q

What is brass made from

A

70% copper

30% zinc

35
Q

What are brass’ special properties

A

Harder than copper, does not corrode

36
Q

What are the uses of brass

A

Musial instruments, ornaments, door knobs and other fittings

37
Q

What is bronze made of

A

95% copper

5% tin

38
Q

Special properties of bronze

A

Harder than brass, does not corrode, chimes when struck

39
Q

Uses of bronze

A

Statues, ornaments, church bells

40
Q

Why have hundreds of aluminium alloys been made?

A

Aircrafts need materials that are light but very strong , and resistant to corrosion. Pure aluminium is light , but not strong enough. So hundreds of aluminium alloys have Been developed, for aircraft parts

41
Q

What is corrosion

A

When a metal is attacked by air, water or other substances in its surrounding is said to make a metal corrode

The more reactive a metal is, the more readily it corrodes

42
Q

What does rusting involve

A

Rusting needs both air and water.

43
Q

The chemical equation for how iron is oxidised.

A

4Fe. +. 302 + 2H20. —> 2Fe2O3H2O

Iron + oxygen + water —> hydrated iron(111) oxide(or rust)

44
Q

How to prevent rusting

A
  1. Coat the metal with something to keep the air and moisture out.

Paint
Grease
Plastics
Another metal

45
Q

What is galvanizing

A

By dipping iron into molten zinc

46
Q

What is the process of tin plating

A

Deposited on the steel by electrolysis

47
Q

How to prevent rusting with chromium

A

Coating with chromium. The chromium is deposited by electrolysis

48
Q

Using sacrificial protection to prevent rusting

A

This is when a more reactive metal is attached to the metal and it corrodes instead of the steel.

49
Q

Does aluminium corrode?

A

No, because a coat of aluminium oxide forms on the aluminium which acts as a seal preventing corrosion

Chemistry (32 decks)

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