Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-Level Chemistry > Organic Chemistry: Alkanes > Flashcards

Organic Chemistry: Alkanes Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

Alkanes

A
  • Saturated (no double C-C bond)
  • Formula - Cn H2n+2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Crude Oil

A
  • Formed from animal and plant remains which are subjected to high pressures and temperatures under the ocean
  • Finite resource
  • Mix of hydrocarbons of different chain lengths
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How and Why does Chain Length impact melting and boiling point of Alkanes?

A
  • Longer chain length = higher melting/boiling point
  • This is because more atoms means more more Van Der Waals forces which need more energy to break
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Fractional Distillation Process

A
  • Crude oil is heated in a furnace
  • A mixture of vapor and liquid is passed through a chamber that is hotter at the bottom and cooler at the top
  • Vapour passes up the chamber via a series of trays containing bubble caps until it reaches a tray that is sufficiently cool where it condenses
  • The mixture of condensed liquids on each tray is piped off
  • Shorter chain hydrocarbons condense in trays near the top of the chamber (cooler, they have lower bp)
  • Bitumen collects at the base of the chamber
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Names and Uses of Fractions

A
  • Bitumen - road surfacing and asphalt for roofs
  • Oil - domestic central heating and ship fuel
  • Kerosene - jet fuel and paint solvent (oil paint)
  • Petrol - fuel
  • Naphtha - used to make drugs, plastics, dyes, explosives and paints
  • LPG (Liquified Petroleum Gas) - used in heating
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Cracking

A

The process of breaking down longer chain hydrocarbons into shorter chain hydrocarbons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why do we need to crack Hydrocarbons?

A

The supply of short chain hydrocarbons isn’t meeting the demand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Types of Cracking

A
  • Thermal Cracking
  • Catalytic Cracking
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Thermal Cracking

A
  • High Temperature (700-1200K)
  • High Pressure (up to 700 kPa)
  • Produces high proportion of alkenes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Catalytic Cracking

A
  • High Temperature (around 700K)
  • Low Pressure
  • Zeolite catalyst
  • Produces mainly branched alkanes, cycloalkanes and aromantic compounds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Advantages and Disadvantages of Thermal Cracking

A

Advantages:
- Produces a high proportion of alkenes
- Can be used for hydrocarbons of any chain length
Disadvantage:
- High temperature and pressure means it’s expensive and uses more energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Advantages and Disadvantages of Catalytic Cracking

A

Advantages:
- Lower temperature and pressure means it’s cheaper and uses less energy
- Produces more arenes and branched alkanes
Disadvantage:
- Can’t be used for all fractions (e.g bitumen, which there is loads of)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why are Alkanes relatively unreactive?

A
  • The bonds in alkanes are relatively strong (van der waals)
  • They are saturated - no double bonds to breaks
  • Non-Polar as carbon and hydrogen have similar electronegativities
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Products of Complete Combustion

A

CO₂ and H₂O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why are combustion of alkanes always exothermic?

A

The amount of energy needed to break bonds is less than the and amount of energy given out when bonds are formed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Fuels

A

Substances that release heat energy when they undergo combustion

17
Q

Incomplete Combustion

A

A limited supply of oxygen during combustion which results in carbon monoxide (CO) and water being formed

18
Q

Carbon Monoxide

A
  • Formed during incomplete combustion
  • CO is a poisonous gas - toxic
19
Q

Nitrogen Oxides

A
  • Produced in engines
  • High temperatures in the engine cause nitrogen to react with oxygen to form nitrogen dioxide
  • The NO₂ then reacts with water vapours and oxygen to form nitric acid
  • Contributes to acid rain and smog
20
Q

Sulfur Dioxide

A
  • Produced from sulfur impurities in crude oil
  • Combines with water vapour and O₂ in the air to form sulfuric acid
  • Contributes to acid rain
21
Q

Carbon Particulates

A
  • Formed during incomplete combustion
  • Exacerbates asthma and causes cancer (carcinogen)
22
Q

Unburnt Hydrocarbons

A
  • Left over from combustion
  • Greenhouse gases
  • Contribute to smog
23
Q

Carbon Dioxide

A
  • Complete combustion
  • Greenhouse gas
  • Always produced when hydrocarbons burn
24
Q

How do you reduce levels of Sulfur Dioxide?

A
  • Flue Gas desulphurisation
  • SO₂ reacts with CaO to form hydrated calcium sulfate
  • CaO(s) + 2H₂O(l) + SO₂(g) + ½O₂(g) –> CaSO₄*2H₂O
25
Q

How do you reduce levels of Carbon Monoxide, Nitrogen Oxides and Unburnt Hydrocarbons?

A
  • Catalytic Converter
  • Honeycomb shape to increase surface area available for reaction
  • 2NO + 2CO → N₂+ 2CO₂
26
Q

Substitution

A

A reaction in which a substituent group is swapped with a new atom

27
Q

Stages of Free Radicalisation

A
  • Initiation
  • Propagation
  • Termination
28
Q

Initiation

A
  • Mixture of Br₂ and CH4
  • UV light is shone at the mixture to break the covalent bonds between Br₂ molecule
  • Br₂ –> 2Br*
29
Q

Propagation

A
  • Br. reacts with CH4 where the Br. bonds with a H atom and takes the electron from the H atom with it to form HBr and CH3.
  • Br. + CH4 –> CH3. + HBr
  • CH3. reacts with Br2 to form CH3Br and Br.
  • CH3. + Br2 –> CH3Br + Br.
30
Q

Termination

A
  • 2 Br. react to form Br2
  • Br. + Br. –> Br2
    OR
  • 2 CH3 . react to form C2H6 (ethane)
  • CH3. + CH3. –> C2H6
    OR
  • A CH3. and a Br. react to form CH3Br (bromomethane)
  • CH3. + BR. –> CH3Br
31
Q

What is the issue with Free Radical Substitution?

A
  • Loads of side products can be formed
  • E.g dibromomethane, tribromomethane and tetrabromomethane
32
Q

What causes the breakdown of Ozone?

A

Ozone reacts with trichlorofluorocarbon (CFCl₃) free radicals and is broken down into oxygen rather than staying as ozone

33
Q

Ozone Breakdown: Initiation

A

CFCl₃ –> CFCl₂ + Cl*

34
Q

Ozone Breakdown: Propagation

A
  • O₃ + Cl* –> ClO* + O₂
  • ClO* + O₃ –>Cl* + 2O₂
35
Q

What are the purpose of the Cl Free Radicals?

A

They act as catalysts

A-Level Chemistry (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions