Brainscape's Knowledge GenomeTM

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


See full index

AQA Chemistry AS level and A level > 12 Alkanes > Flashcards

12 Alkanes Flashcards

1
Q

what are alkanes

A

they are saturated hydrocarbons

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

what are hydrocarbons

A

compounds that only have carbon and hydrogen atoms

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

why are alkanes almost non polar

A

electronegativity of carbon and hydrogen are very similar

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

why does the boling points of alkanes increase with chain length

A

increasing the chain length would mean there are more electrons and the molecule ius getting bigger and so the strength of the van der waals forces increase requiriing more and more nergy to break the intermolecular force as the chain length increases

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

why are alkanes insoluble

A

water molecules are held by strong hydrogen bonds which are much stroner than the van der waals forces that act between the alkane molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

why are alkanes realtively uncreactive

A

the c-c and the c-h bonds are very strong

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

what is petroleum

A

mixture consisting mainly of alkane hydrocarbons that can be separated by fractional distillation.

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

what is the fancy name of petroleum

A

crude oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

explain how fractional distillation is used to sperate crude oil

A

the crude oil is heated in a furnace
the vaporised crude oilfoes into fractionatingf colunms and rises up through the trays.Largest hydrocarbons dont vaporise due its high boiling point and they run to the bottom and collected as residue
the crude oil vapour goes up the fractionating column it gets cooler
as the alkane molecules have different chain lengths lengths they have different boiling points and so the frcations condense at different temperatures and diffrent levels
the hydrocarbons with the lowest boiling points dont condense they are drawn off as gases at the top mof the column

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is cracking

A

the process that breaks some bonds in long chain alkanes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

describe the conditionas and products of catalytic craking

A

uses a zeolite catalyst low tempertaure(720K) and low pressure (just above atmospehric pressure
the products are mainly branched alkanes,cyclohexanes and aromatic compouyndss

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

describe the conditions and products of thermal cracking

A 
high temperature(700-1200K)
high pressure(7000kPa)
produces alkenes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

give an economic reason for cracking

A

to produce substances whihc are more in demand and have a high value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

compare ctalytic cracking with thermal cracking

A

catalytic process more efficent and produces more branched chain molecules than thermal cracking.Branched hydrocarbons burn moe easily and are more useful as fuels.They make better petrol as they dont cause so many probelms in the car engine as they have less sulfur content.They also require less energy for temperature and pressure which decreases costs
catalytic cracking cant be used for very long hydrocarbons because they dont fit into the zeolite whereas thermal cracking can be used for very long hydrocarbons

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

how does the products of complete combustion differ from the products of incomplete combustion

A

complete produces carbon dioxide and water

incomplete produces carbon monoxide and water

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

when does incomplete combustion happen

A

when there is limited supply of oxygen

17
Q

when does complete combustion happen

A

when there is a plentifulk supply of oxygen

18
Q

what is a fuel and give an example

A

a substance that release heat energy when they undergo combustion and also store a large amount of energy for a msall amount of wieght eg.alkanes

19
Q

how is carbon monoxide harmful

A

when its breathed in it combines with haemoglobin in your blood stream.The blood is no longer able to carry oxygen this lack of oxygen causes body and tissue cells to fail and die

20
Q

how are nitrogen oxides harmful

A

they conribute to acid rain ad phtochemical smog

21
Q

how does nitrogen oxides and sulfur dioxide contribute to acid rain

A

they combine with water in the air to form sulfiruc acid/nitric acid and tehy contribute to acid rain

22
Q

how are carbon particulates harmful

A

when breathed in they can worsen asthma and cause cancer

23
Q

how are unburnt hydrocarbons harmful

A

may enter atmosphere can contribute to greenhouse effect and photochemical smog which creates health problems

24
Q

how is carbon dioxide harmful

A

they always produce hydrocarbons and is a greeenhouse gas

its rising level contributes to earths temperature to increase and consequent climate change

25
Q

how is sulfur dioxide harmful

A

they cause pollution air pollution

26
Q

explain and describe how bruning fossil fuels contributes to global warming

A

burning fossil fuels produce carbon dioxide (a greenhouse gas) they absorb infared energy and then they emit some of the energy they abosrb back to earth making it warmer

27
Q

what is carbon nutral activties

A

activties which prodcue no carbon dioxide emissions overall

28
Q

how can gaseous pollutants from internal combustion engines be removed using catalytic converters.

A

catalytic converter is a honeycomb made of a ceramic material coated with platinum and rhodium metals which acts as catalysts.The polluting gases pass over the catalyst and react with each other to form less harmful products
like:
hydrocarbon + nitrogen oxide—> nitrogen + carbon dioxide + water
2CO + 2NO —–> N2 + 2CO2

29
Q

what is flue gas desulfirastion

A

process of removing sulfur dipxide in the atomsphere

30
Q

explain why sulfur dioxide can be removed from flue gases using calcium oxide

A

a slurry of calcium oxide and water is sprayed into suflur dioxide which reacts with the calcium oxide and water to form calcium sulphate which can be further oxidised to calcium sulfate which is a harmless salt

31
Q

what is the chemical recation of sulfur dioxide being removed from flue gases using calcium oxide to form calcium sulfate and giving state symbols

A

CaCO+2H2O +SO2 + 1/2 O2—>CaSO4.2H2O

(g) (g) (g) (g) (s)

32
Q

what is a free radical

A

a particle with an unpaired electron

33
Q

when do free radicals form

A

when a covalent bond splits equally giving one electron to each atom

34
Q

howdoes a halogenoalkane form from the reaction between methane and chlorine

A

CH4 +CL2 —> CH3CL + HCL

initation:
UV
CL2 —> 2CL*

propagation 1 :
CL* + CH4—> CH3* + HCL

propagtion 2:
CH3* + CL2 —> CH3CL + CL*

termincation:
CL* + CH3 —> CH3CL
CH3* + CH3* —> C2H6
CL* + CL* —-> 2CL*

35
Q

why are free radicals highly reactive

A

they have an unpaired electron

36
Q

write chemical equations in initation,propagation1,propagation2 termination only using non radical and free radical

A

initation:non radical —> radical
propagation 1: radical + non radical —> radical + non radical
propagation 2: radical + non radical —> radical + non radical
termination:radical + radical —> non radical

37
Q

why is ozone beneficial

A

it absorbs ultraviolet radiation

AQA Chemistry AS level and A level (12 decks)

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