5 - Chemistry in Industry Flashcards
1
Q
Where are most metals found?
A
- Unreactive = in the ground
- Reactive = in ores
- The more reactive it is the harder it is to extract from a compound
- Ores are finite resources
2
Q
How do you separate metals from their oxides?
A
- Reduction reaction
- Carbon is used as a reducing agent to separate copper oxide
3
Q
Which metals can be extracted using carbon in a reduction reaction?
A
Only metals less reactive than carbon
- Zinc, Iron, Tin
- Heated with carbon monoxide
4
Q
What happens with a more stable ore?
A
The metal is more reactive and difficult to get out of its compound
5
Q
When do you use electrolysis to extract a metal?
A
When it is more reactive than carbon
- Potassium, sodium, calcium, magnesium, aluminium
6
Q
What is aluminium’s ore?
A
Bauxite
- After mining and purifying a white powder is left leaving pure aluminium oxide (Al2O3)
7
Q
How is aluminium extracted from its ore?
A
Electrolysis
- Cryolite lowers the temperature from 2000C to 900C
- This also makes it cheaper to run
- Electrodes are made of graphite
- The positive Al3+ ions attracted to the cathode where they pick up electrons and turn into aluminium ions (which sink to the bottom)
- The negative O2- ions are attracted to the anode where they lose electrons and react with oxygen or carbon to form O2 or CO2
- The anode gets worn down from the reacting oxygen so needs to be replaced
8
Q
What are the half equations in the electrolysis of aluminium?
A
Anode: 2O2- –> O2 + 4e- (oxidation)
Cathode: Al3+ + 3e- –> Al (reduction)
A redox reaction
9
Q
Why is electrolysis of aluminium expensive?
A
- Uses lots of electricity
- Needs lots of heat
- The anode needs constant replacing
10
Q
What are the raw materials needed in the extraction of iron?
A
Iron ore - iron
Coke (pure carbon) - reduction agent
Limestone - removes impurities in the form of slag
11
Q
Describe the extraction of iron
A
- Hot air is blasted into the furnace
- Temperature = 1500*C
- Coke burns to produce CO2 (C + O2 –> CO2)
- The CO2 reacts with the unburnt coke to form CO2 (CO2 + C –> 2CO)
12
Q
Describe the extraction of iron
A
- Hot air is blasted into the furnace
- Temperature = 1500*C
- Coke burns to produce CO2 (C + O2 –> CO2)
- The CO2 reacts with the unburnt coke to form CO2 (CO2 + C –> 2CO)
- The carbon monoxide reduces the iron ore to iron (3CO + Fe2O3 –> 3CO2 + 2Fe
- The iron is molten at this temperature and is very dense so runs to the bottom of the furnace and is tapped off
13
Q
How are impurities removed in the extraction of iron?
A
- The main impurity is sand (silicon dioxide) which has a very high melting point
- The limestone is decomposed by the heat into calcium oxide and CO2 (CaCO3 –> CaO + CO2
- The calcium dioxide reacts with the sand to form calcium silicate (slag) which is molten and tapped off (CaO + SiO2 –> CaSiO3)
- The cooled slag is used for road building or in fertilisers
14
Q
What are some properties of aluminium and iron?
A
- Both dense and lustrous (shiny)
- High melting points
- Hard and strong
- Malleable (can be hammered into a different shape)
- Good conductors of heat and electricity
15
Q
What are some uses of iron?
A
- Wrought iron is pure iron and is malleable so is used for ornamental gates and railings
- Cast iron (iron, carbon, silicon) is hard but brittle so used for manhole covers and cooking pans
- Steel (iron and carbon) is very hard so used for car bodies and girders
- Stainless steel (iron and chromium) is used for cutlery and cooking pans
16
Q
What are some problems with iron?
A
- It corrodes easily
17
Q
What are some uses of aluminium?
A
- Fizzy drink cans because it doesn’t corrode when in contact with water
- In bicycle frames and aeroplanes because it is light and malleable
18
Q
What are some uses for refinery gases?
A
- Bottled gas
- Heating
- Pottery
- Glass manufactures
19
Q
What are some uses for refinery gases?
A
- Bottled gas
- Heating
- Pottery
- Glass manufactures
20
Q
What are some uses for gasoline?
A
Fuel for cars
21
Q
What are some uses for Naphtha?
A
- Plastics
- Paints
- Dyes
- Drugs
- Explosives
22
Q
What are some uses for kerosene (paraffin)?
A
- Jet engines
- Domestic heating
- Paint solvent
23
Q
What are some uses for diesel?
A
Fuel for diesel engines in cars, trucks, trains, boats, etc
24
Q
What are some uses for fuel oil?
A
- Domestic central heating
- Fuel for big ships
25
What are some uses for bitumen?
- Road surfacing
| - Asphalt for roofs
26
What are the products of crude oil?
- Bitumen
- Fuel oil
- Diesel
- Kerosene (paraffin)
- Naphtha
- Gasoline
- Refinery gases
27
Fractional distillation of crude oil
- A physical process (no chemical reactions)
- Heated to the boiling point of the highest component
- Separated into different hydrocarbon fractions
- The longer the hydrocarbon the higher the boiling point
- Bubble caps stop them from running back down
28
How are pollutants produced?
By burning fuels (e.g. carbon monoxide, nitrogen oxides, sulphur dioxides, etc)
29
How is carbon monoxide produced?
- Formed when hydrocarbon fuels (e.g. petrol or diesel) are burnt without enough oxygen = incomplete combustion
- Poisonous as it combines with haemoglobin in blood cells so not as much oxygen can be carried
- Can lead to fainting, coma or death
30
How is sulphur dioxide and nitrogen oxides produced?
- When fossil fuels are burnt
- Sulphur dioxide comes from sulphur impurities in fossil fuels
- Nitrogen oxides are created when the temperature is high enough from nitrogen and oxygen in the air to react
31
How is acid rain caused?
- When sulphur dioxide mixes with clouds to form dilute sulphuric acid
- Nitrogen oxide can also form nitric acid in clouds
- Acid rain causes lakes to become acidic
- Kills trees and damages limestone buildings
32
Why is all rain slightly acidic?
Because carbon dioxide in the air reacts with water to produce a slightly acidic solution
33
Why is all rain slightly acidic?
Because carbon dioxide in the air reacts with water to produce a slightly acidic solution
34
How are hydrocarbons split?
By cracking which is a form of thermal decomposition as it breaks down molecules into simpler molecules through heat
- Produces alkenes which are used to make polymer
35
Describe the conditions for cracking of hydrocarbons
- Vaporised hydrocarbons are passed over a powdered catalyst
- Catalyst = Silica (SiO2) and alumina (Al2O3)
- Temperature = 600 - 700*C
36
Describe the cracking of paraffin in the lab
- Heat the paraffin and silica and alumina alternatively until the paraffin vaporises and the catalysts glow red
- The heated paraffin cracked when passed over the heated catalyst
- Small alkanes collect at the end of the boiling tube while alkene gases travel down the delivery tube
- The alkenes are collected through water using a gas jar
- Always makes an alkane and alkene
37
Why is the Haber process used?
To make ammonia from nitrogen and hydrogen
38
What are the conditions in the Haber process?
Nitrogen = air
Hydrogen = natural gas or from cracking hydrocarbons
Pressure = 200 atmospheres
Temperature = 450*C
Catalyst = Iron
- it is a reversible reaction (forward = exothermic)
39
Describe the reversible reaction in the Haber process
- High pressure favours the forward reaction so pressure as high as possible
- The forward reaction is exothermic so needs a lower temperature
- Low temperature = slow reaction
- 450*C is a compromise between high yield and high speed
- The unused hydrogen and nitrogen are recycled so nothing is wasted
40
What are some uses for ammonia?
- In the Ostwald process to make nitric acid
- You can react ammonia with nitric acid to get ammonium nitrate
- Good for fertilisers because it has nitrogen from two sources so more concentrated and is more effective than organic fertilisers
41
Why is the Contact Process used?
To make sulphuric acid
42
Describe the Contact Process
- Sulphur is burnt in air or sulphide ores are roasted to make sulphur dioxide (s + O2 --> SO2
- The sulphur dioxide is oxides to form sulphur trioxide (2So2 + O2 2SO2)
- The sulphur trioxide is dissolved in concentrated sulphuric acid to form liquid oleum (SO3 + H2SO4 --> H2S2O7)
- The oleum is diluted with water to form concentrated sulphuric acid (H2S2O7 + H2O --> 2H2SO4)
43
What are the conditions for the Contact Process?
```
Temperature = 450*C
Pressure = 2 atmospheres
Catalyst = Vanadium(V) oxide (V2O5)
```
44
What are some uses for sulphuric acid?
- Fertilisers = mostly in phosphate fertilisers
- Detergents
- Paints = used to make titanium dioxide which is a white pigment in paints
45
Describe the electrolysis of brine
- Carbon electrodes
- Hydrogen gas is given off at the cathode (two hydrogen ions accept two electrons to become one hydrogen molecule)
- Chlorine gas is given off at the anode (two chloride ions lose their electrons to become one chlorine molecule)
- The sodium ions and hydroxide ions from the water stay in the solution leaving sodium hydroxide
46
What are the half equations for the electrolysis of brine?
Cathode = 2H+ + 2e- --> H2
| Anode 2Cl- --> Cl2 + 2e-
47
What are the half equations for the electrolysis of brine?
Cathode = 2H+ + 2e- --> H2
| Anode 2Cl- --> Cl2 + 2e-
48
What are some uses of chlorine?
- Used to sterilise water supplies
- To make bleach
- To make HCl
49
What are some uses of hydrogen?
- In the Haber process
- To change oils into fats
- For making margarine
50
What are some uses of sodium hydroxide?
- It is a strong base
- Used to make soaps
- Used to make bleach
- Used to make paper pulp
51
What are the products from the electrolysis of brine?
- Chlorine gas
- Hydrogen gas
- Sodium hydroxide solution
