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organic chemistry Flashcards

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1
Q

Formation of crude oil

A

Made from remains of marine plants and animals - mostly plankton - that died millions of years ago

Remains sank to bottom of sea and were buried by layers of sand and mud, preventing them from rotting

Layers gradually became sedimentary rock

Over millions of years, layers of rock built up increasing the heat and pressure, breaking remains into CRUDE OIL.

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2
Q

Crude oil is a mixture of molecules called what?

A

Hydrocarbons

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3
Q

what is a hydrocarbon (definition)

A

Hydrocarbons are molecules made up of hydrogen and carbon atoms only

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4
Q

what is one hydrocarbon in crude oil

A

methane

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5
Q

methane formula

A

CH4

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6
Q

what kind of resource is crude oil and where found

A

finite, found in rocks

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7
Q

besides methane, what other hydrocarbon is found in crude oil

A

ethane

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8
Q

what do scientists call hydrocarbons like ethane and methane

A

alkanes

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9
Q

what is the general formula of alkenes

what this means

A

CnH2n+2

this means that if we know the numb of carbon atoms in the alkene (n), then we can calculate the number of hydrogen atoms
to do that ,we calculate the number of hydrogen atoms by 2 and then add 2

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10
Q

propane is an alkene with 3 carbon atoms.
work out the number of hydrogen atoms
then write the formula

A

8

formula = C3H8

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11
Q

what are alkanes and why

A

saturated molecules

because the carbon atoms are fully bonded to hydrogen atoms

(for my own info, alkenes are a family of hydrocarbons)

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12
Q

what are the first four alkanes

A

methane
ethane
propane
butane

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13
Q

methane structure

A 
H
            l
      H - C - H
             l
            H
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14
Q

Ethane structure

A 
H    H
            l      l
      H - C - C - H
             l     l
            H    H
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15
Q

Propane structure

A 
H    H   H
            l      l     l
      H - C - C - C - H
             l     l     l
            H    H   H
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16
Q

Butane structure

A 
H    H   H   H
            l      l     l    l
      H - C - C - C - C - H
             l     l     l     l
            H    H   H   H
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17
Q

what does viscosity tell us

fluids with a high viscosity flow …

fluids with a low viscosity flow ….

A

the thickness of a fluid

slowly

quickly

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18
Q

as the size of hydrocarbons increase, what happens to the viscosity of the molecules

so very long chains of hydrocarbon flow very …..

but short chains flow…./

A

they get more viscous

slowly - they r extremely viscous

quickly

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19
Q

what does flammability tell us

A

how easily a hydrocarbon combusts (burns)

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20
Q

how flammable are short chain hydrocarbons

A

extremely flammable

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21
Q

what gas is used in bunsen burners

A

methane

22
Q

as the size of hydrocarbons increase, the molecules get more or less flammable

A

less

23
Q

are long chain hydrocarbons difficult to burn

A

yes.

24
Q

what is the boiling point

A

the temp at which a liquid turns to gas

25
Q

do short chain hydrocarbons have low or high boiling points

A

low

26
Q

the first four alkenes are gases at room temp, why

A

because they all have boiling points which are lower than room temp

27
Q

when do hydrocarbon fuels release energy

A

when combusted (burned)

during combustion, thecarbon and hydrogen atoms in the fuel react with oxygen. The carbon and hydrogen are oxidised

28
Q

when hydrocarbon fuels release energy when combusted, if this oxygen is unlimited then what does it produce and what is this called

A

carbon dioxide and water

called complete combustion

29
Q

what do we have to do in order for hydrocarbons to be useful

A

seperate them

30
Q

how do we separate hydrocarbons

A

using fractional distillation

31
Q

In fractional distillation, crude oil is separated into ….. Fractions contain hydrocarbons with a similar number of …… …..

A

fractions

carbon atoms

32
Q

where does fractional distillation take place in

A

very large columns which are found in oil refinaries

33
Q

steps of fractional distillation of crude oil

A

Crude oil heated to high temp, causing it to boil - all hydrocarbons evaporate and turn into gas

crude oil vapour is then fed into fractional distillation column

column is hotter at bottom and cooler at top

hydrocarbon vapours rise up column

hydrocarbons condense (turn to liquid) when they reach their boiling point, aka they turn back to liquid

Liquid fractions are then removed

remaining hydrocarbons keep moving up column

These condense when they reach their boiling points

34
Q

very long chain hydrocarbons have what

A

very high boiling points

35
Q

in fractional distillation, long chain hydrocarbons have high boiling points. Where are they removed from?

A

From the bottom of the column

36
Q

short chain hydrocarbons have low boiling points. in fractional distillation, these do not condense. Where are they removed from and as what

A

removed from the top of the column as gases

37
Q

Fractional distillation produces what which contain what

A

fractions which contain hydrocarbons with a similar number of carbon atoms

38
Q

some fractions are used as fuels. Give some examples

A

petrol and diesel to fuel cars or liquified petroleom gas in camping stoves

39
Q

Some fractions are used as feedstock for the petrochemical industry. What is a feedstock

A

A chemical used to make other chemicals

40
Q

general formula of alkanes

A

CnH2n+2

41
Q

between the carbon atoms, what kind of bond do alkanes have

A

alkanes only have single covalent bonds between the carbon atoms

42
Q

name one reason as to why long-chain hydrocarbons do not make good fuels

A

because long chain hydrocarbons are not very flammable

this is a problem because there is such a high demand for short-chain hydrocarbons to be used as fuels

43
Q

to solve our problem of there being such a high demand for short chain hydrocarbons to be used as fuels since long chained hydrocarbons are not flammable, what should be done

A

convert long chain hydrocarbons into shorter chain hydrocarbons

TO DO THAT WE USE A PROCESS CALLED CRACKING!

44
Q

What happens in cracking…?

A

A long-chain alkane is broken down (cracked) to produce smaller, more useful molecules

45
Q

conditions for cracking…./what are the two ways we can carry out cracking… one of them is called catalytic cracking, what happens here

A

In catalytic cracking, we use high temperature and a catalyst (job of the catalyst is to speed up the reaction)

46
Q

conditions for cracking…./what are the two ways we can carry out cracking… another of them is called steam cracking…what happens here?

A

In steam cracking, we use high temperature and steam

47
Q

what does cracking make

A

hydrocarbons called alkenes

48
Q

what kind of bond do alkenes have between two carbon atoms

A

alkenes have a double covalent bond between two carbon atoms

49
Q

alkenes are very useful molecules. why?

A

Firstly, alkenes are used to make chemicals called polymers

Alkenes are also used as a starting material for other useful chemicals as well

50
Q

are alkenes more or less reactive than alkanes

A

Alkenes are MORE reactive than alkanes

51
Q

One key fact about alkenes is that they are more reactive than alkanes.
We can use this to test for alkenes and it is really important to learn this test….

A

we test for alkenes using bromine water which is orange.

If we shake our alkene with bromine water, then the bromine water turns COLOURLESS

52
Q

ALSO remember to learn all the molecular formulas and stuff for alkanes and alkene like ethene/ethane etc

A

yes

chemistry (11 decks)

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