Topic 6: Global Challenges Flashcards
1
Q
What are alkanes?
A
- Group of saturated hydrocarbons (only contain hydrogen and carbon)
Saturated: Only have single carbon-carbon bonds
2
Q
What is the general formula for alkanes?
A
CₙH₂ₙ₊₂
3
Q
How reactive are alkanes?
A
- Generally unreactive compounds but undergo combustion reactions
- Can be cracked into smaller more useful molecules
4
Q
List the first 5 members of the alkane series
A
Methane- CH₄
Ethane- C₂H₆
Propane- C₃H₈
Butane- C₄H₁₀
Pentane- C₅H₁₂
5
Q
What happens during the complete combustion of alkanes?
A
Complete combustion of alkanes produces water (H₂O) and carbon dioxide (CO₂).
Example: CH₄ + 2O₂ → CO₂ + 2H₂O.
6
Q
What is the main component of gasoline, and what is its combustion equation?
A
Gasoline is mainly composed of octane (C₈H₁₈). Its combustion equation is:
2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O.
7
Q
Why do car engines produce unburnt hydrocarbons and other harmful products?
A
Inefficient combustion in car engines leads to unburnt hydrocarbons, carbon monoxide, and soot, which cause environmental problems
8
Q
What environmental issue is caused by carbon dioxide from combustion engines?
A
Carbon dioxide (CO₂) from combustion engines contributes to global warming, driving the need for electric vehicles
9
Q
What are alkenes?
A
- Unsaturated hydrocarbons
- Contain a double carbon bond which allows them to react in ways alkanes cannot
10
Q
List the first 4 members of the alkene series
A
Ethene- C₂H₄
Propene- C₃H₆
But-1-ene- C₄H₈
Pent-1-ene- C₅H₁₀
11
Q
What is the meaning of the numbers in some of the alkenes?
A
Numbers can be found in butene, pentene and hexene as they refer to the carbon atom the double bond begins
12
Q
Why are alkenes more reactive than alkanes?
A
- Have a C=C double bond
- Can open up the bond to make more bonds with atoms by allowing incoming atoms to form another single bond with each carbon atom
- This means each carbon atom now forms 4 single bonds instead of 1 double bond and 2 single bonds
13
Q
Describe the complete combustion of alkenes
A
- Occurs in excess oxygen
- Produces carbon dioxide (CO₂) and water (H₂O)
Example:
C₄H₈ + 6O₂ → 4CO₂ + 4H₂O
14
Q
Describe the incomplete combustion of alkenes
A
-Occurs in limited oxygen
-Produces carbon monoxide (CO), water (H₂O), and/or soot (C)
Example:
C₄H₈ + 4O₂ → 4CO + 4H₂O
or
C₄H₈ + 2O₂ → 4C + 4H₂O
-Higher alkenes produce smokier, yellow flames
15
Q
Name the two types of addition reactions alkenes undergo
A
Hydrogenation & Halogenation
16
Q
Describe Hydrogenation
A
- Where an alkene undergoes an addition reaction with hydrogen in which an alkane is formed
- Occurs at 150ºC using a nickel catalyst
- C=C +H₂ →C-C (alkane)
17
Q
Describe Halogenation
A
- Where an alkene undergoes an addition reaction with halogens (e.g Cl₂, Br₂) in which a dihaloalkane is formed
- Occurs at room temp. with no catalyst as halogens are highly reactive
- C=C+X₂ →C-C (dihaloalkane)
18
Q
What can be used to differentiate alkanes and alkenes?
A
- As alkenes have a C=C double bond, they can react in ways alkanes cannot
- This means we can tell them apart using a Bromine Water Test
19
Q
What is a bromine water test?
A
- Orange coloured solution
- When added to an alkane, will remain orange as bromine has nothing to attach to and remains in solution
- When added to an alkene, bromine atoms add across C=C bond, causing solution to no longer contain free bromine and turn colourless
20
Q
What are polymers?
A
- Polymers are large molecules with high relative molecular mass, made by linking together smaller molecules called monomers (repeat unit connected by covalent bonds)
21
Q
Name 3 different types of polymers
A
Synthetic, Natural and Biological
22
Q
Name some examples of Synthetic Polymers
A
Resins, Plastics, Polystyrene, Nylon
23
Q
How are addition polymers formed?
A
- Joining up of many monomers and only occur in monomers that contain C=C bonds (alkene)
24
Q
How do you deduce a monomer from a polymer?
A
- Identify the repeat unit in the polymer structure
- Locate the single bond in the repeat unit that was originally a double bond in the monomer
- Change the single bond back to a double bond
- Remove the continuation bonds (bonds extending outside the brackets)
- Adjust the remaining groups to match the structure of the monomer
25
What is crude oil?
- Finite resource found in Earth's crust
- Thick, sticky, black liquid that is found in porous rock (under the ground and under the sea)
- Also known as petroleum
- Complex mixture of hydrocarbons which also contains natural gas
26
What do the molecules of crude oil consist of?
- Consist of carbon backbone (ring or chain)
- Hydrogen atoms attached to carbon atoms
- Contains many different ring sizes and chain lengths
27
How did crude oil form?
- Formed over millions of years from the effects of high pressures and temperatures on the remains of plants and animals
28
Why is crude oil finite?
It is being used up much faster than it is being formed, which is why we say crude oil is a finite resource
29
What is a hydrocarbon?
Compound which consist of carbon and hydrogen atoms only
30
Why is crude oil not useful as a mixture, but its fractions are valuable?
- Crude oil is a mixture of many different hydrocarbons.
- The fractions (groups of hydrocarbons with similar chain lengths) are separated and have many useful applications.
31
What is fractional distillation, and how does it work?
- Fractional distillation is the process of separating crude oil into its fractions based on their boiling points.
- It occurs in a fractionating column:
>Hot at the bottom, cool at the top.
>Hydrocarbons with high boiling points condense at the
bottom.
- Hydrocarbons with low boiling points condense at the top.
32
How does the size of a hydrocarbon molecule affect its boiling point?
- Larger hydrocarbons (more carbon atoms) have higher boiling points.
- This is because intermolecular forces are stronger in larger molecules, requiring more energy to break.
33
Where are different fractions collected in the fractionating column?
- Smaller hydrocarbons (low boiling points): Collected at the top as gases.
- Larger hydrocarbons (high boiling points): Collected at the bottom as liquids.
34
What type of hydrocarbons are most fractions made of?
Most fractions contain alkanes: hydrocarbons with only single bonds between carbon atoms.
35
Why are fractions valuable?
Each fraction has different applications, such as fuels, lubricants, and raw materials for chemicals.
36
What does a fractional distillation diagram show?
A fractionating column with:
> Crude oil entering and being heated.
> Vapours rising and condensing at different heights based on boiling points.
> Fractions being tapped off at different levels.
37
What is the difference between saturated and unsaturated molecules?
- Saturated molecules: Contain only single bonds (e.g., alkanes).
- Unsaturated molecules: Contain double bonds (e.g., alkenes).
38
What is cracking, and why is it used?
- Cracking is the process of breaking down long-chain alkanes into shorter-chain molecules.
- It produces smaller alkanes, alkenes, and hydrogen, which are more useful (e.g., petrol, ethene for plastics).
39
What are the conditions required for cracking?
- Heat hydrocarbons to 600–700°C to vaporise them.
- Pass vapours over a hot catalyst (e.g., alumina or silica).
- This causes thermal decomposition, breaking covalent bonds randomly.
40
What are the main products of cracking?
- Smaller alkanes (e.g., petrol).
- Alkenes (e.g., ethene for plastics).
- Hydrogen gas.
41
What is an example of a cracking reaction?
- Hexane is cracked to produce butane (fuel) and ethene (for plastics):
C₆H₁₄ → C₄H₁₀ + C₂H₄
42
What are the uses of cracking products?
- Alkanes (e.g., butane): Used as fuels.
- Alkenes (e.g., ethene): Used to make plastics and ethanol.
- Hydrogen: Used in industrial processes.
43
Why are kerosene and diesel often cracked?
To produce petrol, alkenes, and hydrogen, which are more valuable and useful.
44
What should you check when writing cracking equations?
- Ensure the number of carbon and hydrogen atoms balances on both sides.
- Ensure the products are either alkanes (CnH₂n₊₂) or alkenes (CnH₂n).
45
What is the contact process?
Process used to manufacture sulfuric acid which is important in the manufacture of fertiliser
46
What are some other uses of sulfuric acid other than as fertiliser?
- Metal Treatment
- Drug Manufacturing
- Making Paint and Dyes
- Making of Explosives
47
What is Stage 1 of the Contact Process?
Sulfur is burned in oxygen to produce sulfur dioxide:
S (s) + O2 (g) → SO2 (g)
48
What is Stage 2 of the Contact Process?
Sulfur Dioxide and oxygen react to form sulfur trioxide:
2SO2 (g) + O2 (g) ⇌ SO3 (g)
49
What are the reaction conditions for Stage 2 of the Contact Process?
- Temperature of 450ºC
- Pressure of 2 atmospheres (200 kPa)
- Vanadium Oxide Catalyst, V₂O₅
50
What elements are needed for plant growth and what are they for?
- Nitrogen: Healthy Leaves
- Potassium: Growth, healthy fruit and flowers
- Phosphorus: Healthy Roots
51
What happens if there are limited key elements in soil?
Yield of crop is reduced
52
What fertiliser do farmers normally use and why?
- NPK fertilisers
- Formulations has appropriate ratio of 3 elements
53
Why can't plants use nitrogen from the air?
Plant roots only absorb elements in water soluble form
54
Name some common fertilisers and the essential elements they contain
Ammonium Nitrate- NH₄NO₃- Nitrogen
Ammonium Sulfate- (NH₄)₂SO₄- Nitrogen
Ammonium Phosphate- (NH₄)₃PO₄- Nitrogen, Phosphorus
Potassium Nitrate- KNO₃- Potassium, Nitrogen
55
What are the two ways to make fertilisers?
- Made in a lab
- Made industrially
56
How is ammonia sulfate prepared industrially?
Haber Process
57
How is sulfuric acid prepared industrially?
Contact Process
58
What is the key difference between industrial and lab-scale fertiliser production in terms of process type?
Industrial fertiliser production is a continuous process, while lab-scale production is a batch process.
59
What is a continuous process in industrial fertiliser production?
A continuous process means the product is made all the time as long as raw materials are available, allowing for large quantities to be produced.
60
What is a batch process in lab-scale fertiliser production?
A batch process involves making a small amount of fertiliser at a time, with equipment cleaned before the next batch is started.
61
How do industrial fertiliser factories operate in terms of processes?
They have many integrated processes happening simultaneously to produce multiple fertilisers at the same time.
62
What are some raw materials used in industrial fertiliser production?
Raw materials include sulfur (to make sulfuric acid) and phosphate rock (to make phosphoric acid).
63
Why can industrial fertiliser factories produce large quantities?
Because they operate continuously and have integrated processes that allow for simultaneous production of multiple fertilisers.
64
Why can phosphate rock not be used as a fertiliser?
Insoluble in water
65
What are the two sources of most salts in NPK fertilisers?
- Mined
- Manufactured by reacting acid with base
66
In what other wat is ammonia used to make salts for fertilisers which is not ammonium salts?
Oxidising ammonia to make nitric acid for ammonium nitrate and potassium nitrate
67
Which salts are in single superphosphate?
- Calcium Sulfate
- Calcium Phosphate
68
Which salts are in triple superphosphate?
- Calcium Phosphate
69
Name some salts which are mined with their formula.
Potassium Chloride- KCl
Potassium Sulfate- K₂SO₄
70
Name some salts which are manufactured with their formula, what acid it is made from and what it reacts with.
Ammonium Nitrate- NH₄NO₃- Ammonia and Nitric Acid
Ammonium Sulfate- (NH₄)₂SO₄- Ammonia and Sulfuric Acid
Ammonium Phosphate- (NH₄)₃PO₄- Ammonia and Phosphoric Acid
Calcium Nitrate- Ca(NO₃)₂- Limestone and Nitric Acid
Calcium Phosphate- Ca₃(PO₄)₂- Phosphate Rock and Phosphoric Acid
Calcium Sulfate- CaSO₄- Phosphate Rock and Sulfuric Acid
71
What is the difference in rate of production between a batch and continuous process?
Batch- Low
Continuous- High
72
What is the difference in relative cost of equipment between a batch and continuous process?
Batch- Low
Continuous- High
73
What is the difference in number of workers between a batch and continuous process?
Batch- Large
Continuous- Small
74
What is the difference in shut-down periods between a batch and continuous process?
Batch- Frequent
Continuous- Rare
75
What is the difference in ease of automating the process between a batch and continuous process?
Batch- Low
Continuous- High
76
How is ammonia manufactured?
Haber Process
77
What is 80% of the ammonia produced used for?
Production of fertiliser
78
What the reactants in the Haber Process and where are they extracted from?
Hydrogen- Methane
Nitrogen- Air
79
What are the 5 stages of the Haber Process?
Stage 1- H₂ and N₂ gases are pumped into the compressor through pipes
Stage 2- The gases are compressed to about 200 atmospheres inside the compressor
Stage 3- The pressurised gases are pumped into a tank containing layers of catalytic iron beads at a temperature of 450°C. Some of the hydrogen and nitrogen react to form ammonia in the following reversible reaction
N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)
Stage 4- Unreacted H2 and N2 and product ammonia pass into a cooling tank.
The ammonia is liquefied and removed to pressurised storage vessels
Stage 5- The unreacted H2 and N2 gases are recycled back into the system
80
What are the conditions needed in the Haber Process?
- Pressure of 200 atmospheres
- Temperature of 450°C
- Iron Catalyst
81
What do the conditions of the Haber Process produce a yield of?
Equilibrium Yield of ammonia of about 30%
82
Why is a pressure of 200 atmospheres used in the Haber Process?
- Compromise
- High pressures would shift the equilibrium to the right due to there being less molecules on the right hand side of the equation resulting in a higher yield
- Very high pressures are hazardous and expensive so a lower pressure is used to reduce the risk
83
Why is a temperature of 450°C is used?
- Compromise
- The forward reaction is exothermic so a low temperature would shift the equilibrium to the right increasing the yield of ammonia
- Low temperatures, however, result in a slower rate of reaction
- The higher temperature allows ammonia to be made within a reasonable time frame
84
What should manufacturers consider when there are multiple methods for producing the same substance?
- Consider raw materials used
- Amount of energy required for process
85
What are ores and why are they important in metal extraction?
Ores are rocks containing enough metal to make extraction worthwhile. Examples include haematite (iron) and bauxite (aluminium).
86
How are unreactive metals like gold extracted?
They are found as uncombined elements (native metals) and mined directly from the Earth’s crust.
87
How does the reactivity series determine extraction methods?
Metals above carbon (e.g., aluminium) are extracted by electrolysis. Metals below carbon (e.g., iron) are extracted by heating with carbon (reduction).
88
Describe the two-stage extraction of copper from copper(II) sulfide.
1. Stage 1: Heated in air to form copper(II) oxide: 2CuS(s) + 3O₂(g) → 2CuO(s) + 2SO₂(g). 2. Stage 2: Reduced by carbon: 2CuO(s) + C(s) → 2Cu(s) + CO₂(g).
89
What are the raw materials in a blast furnace?
Iron ore (haematite, Fe₂O₃), coke (carbon), and limestone (CaCO₃).
90
Summarize the reactions in each zone of the blast furnace.
Zone 1: C + O₂ → CO₂. Zone 2: CO₂ + C → 2CO. Zone 3: Fe₂O₃ + 3CO → 2Fe + 3CO₂.
91
What is the role of limestone in the blast furnace?
Removes impurities (e.g., SiO₂) by forming slag (CaSiO₃): CaCO₃ → CaO + CO₂; CaO + SiO₂ → CaSiO₃(l).
92
Why is cryolite used in aluminium extraction?
It lowers the melting point of aluminium oxide (Al₂O₃), reducing energy costs.
93
Write the electrode reactions in aluminium extraction.
Cathode: Al³⁺ + 3e⁻ → Al. Anode: 2O²⁻ → O₂ + 4e⁻.
94
Why are graphite anodes replaced regularly in aluminium extraction?
They react with oxygen to form CO₂.
95
What are phytoextraction and bioleaching?
Phytoextraction: Plants absorb metals, which are concentrated in shoots/leaves, harvested, burned, and extracted. Bioleaching: Bacteria break down ores into acidic leachates containing metal ions (e.g., Cu²⁺).
96
Give two advantages of biological extraction methods.
1. Less environmental damage vs. traditional mining. 2. Can extract metals from low-grade ores or waste.
97
Why is recycling metals beneficial?
Conserves finite resources (e.g., iron ore). Reduces landfill waste and energy use vs. extraction.
98
How is glass recycled?
Sorted by color, crushed, melted, and remoulded.
99
What conditions are needed for rusting?
Oxygen + water (accelerated by salt). Equation: 4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O.
100
How does sacrificial protection work?
A more reactive metal (e.g., zinc) corrodes first, losing electrons instead of iron.
101
Why are alloys harder than pure metals?
Different-sized atoms distort layers, preventing sliding.
102
Match alloys to uses.
Bronze (Cu + Sn): Bells, ship propellers. Steel (Fe + C): Buildings (high strength). Solder (Sn + Cu): Joining pipes (low MP).
103
Give two properties of ceramics.
Hard, high MP, thermally resistant (e.g., bricks).
104
Why is PVC used for insulation?
Polymers are poor conductors of heat/electricity.
105
What are composites made of?
Reinforcement (e.g., fibres) + matrix (binder). Example: Fibreglass (glass fibres + polymer resin).
106
What are the 4 stages of LCA?
Raw materials → Manufacture → Usage → Disposal.
107
Compare plastic vs. paper bags in LCA.
Plastic: Non-biodegradable but reusable. Paper: Biodegradable but energy-intensive to make.
108
List the reactivity series (from most to least reactive) and state the extraction method for metals above/below carbon.
1. Most Reactive: K, Na, Li, Ca, Mg, Al → Electrolysis. 2. Carbon (C). 3. Zn, Fe, Pb, Cu, Ag, Au → Heating with carbon. 4. Least Reactive: Au → Found native.
