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IGCSE Chemistry- Part 3 > Organic chemistry > Flashcards

Organic chemistry Flashcards

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1
Q

what is crude oil?

A

a thick, sticky, black liquid that is found under the ground and under the sea in certain parts of the world. eg. middle east and texas

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2
Q

what are the products of complete and incomplete combustion?

A
  • complete combustion gives carbon dioxide and water

- incomplete combustion gives carbon monoxide and water

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3
Q

what is the trend between boiling point and viscosity?

A
  • lower down the fractionating column, the higher the boiling point
  • the higher the boiling point, the lower the viscosity, the lower the boiling point, the higher the viscosity
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4
Q

what is viscosity?

A

the state of being thick, sticky, and semi-fluid in consistency, due to internal friction

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5
Q

what are the names and uses of the main fractions obtained from crude oil?

A
  • refinery gases- bottled gas for camping etc
  • gasoline- petrol for cars
  • kerosene- fuel for aeroplanes
  • diesel oil- fuel for buses, trucks, trains and cars
  • fuel oil- fuel for ships and industrial heating
  • bitumen- road surfaces and covering flat roofs for buildings
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6
Q

what is the general formula for alkenes?

A

the alkenes are homologous series compounds that have the general formula CnH2n

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7
Q

describe the addition reaction of alkenes with bromine

A

an alkene will make its double bond into a single bond, to bond two bromines. Bromine (red/brown) is added to the molecule. The product made is colourless. When alkenes are put in bromine water it turns from brown to colourless (a good way of testing for alkenes). For example:
C2H4(g)+Br2(aq)=C2H4r2(aq)
saturated compounds such as alkanes will not decolourise bromine water. There is no double bond, so no more atoms can be added to the molecule

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8
Q

how are two long-chain alkanes converted to alkenes and shorter-chain alkanes by catalytic cracking?

A

long-chain hydrocarbons are passed over a hot catalyst (silica or alumina at 600-700°). This causes them to break down into smaller molecules. As some are lost from molecules, they become unsaturated and can therefore form a double bond. This is how you get alkenes from the process as well as shorter chain alkanes.

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9
Q

describe the manufacture of ethanol by the fermentation of sugars

A

ethanol can be made by the anaerobic respiration of microorganisms. Glucose=ethanol+carbon dioxide. This happens at 30°

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10
Q

what are the factors relevant to the choice of method used in the manufacture of ethanol?

A 
fermentation:
- cane sugar widely available/cheap/renewable
- slow process
- impurities in the product
- done in batches
Hydrating (ethene and steam):
- crude oil (cracked to make ethene) expensive/non-renewable
- fast process
- pure product
- continuous reaction
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11
Q

how is an addition polymer formed?

A

monomers are alkenes with a double bond. If this bond is broken there can be other things bonded, if a carbon from another monomer is bonded in then you can create a chain; do this many times and you have a polymer.

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12
Q

how does fractional distillation separate crude oil into fractions?

A
  1. fractional distillation is carried out in a fractionating column. The column is hot at the bottom and gradually becomes cooler at the top
  2. the crude oil is split into various fractions. A fraction is a mix of hydrocarbons with very similar boiling points
  3. Crude oil is heated to convert it into a vapour. The vapour is then fed into the bottom of the fractionating column
  4. The hydrocarbons with very high boiling points (fuel, oil and bitumen) immediately turn into liquids and are tapped off at the bottom of the column
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13
Q

what are alkanes?

A

alkanes contain a single chain of carbon atoms with hydrogen atoms bonded along the side

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14
Q

how does incomplete combustion produce carbon monoxide?

A

incomplete combustion of an alkane produces carbon monoxide. The same is true when petrol or diesel is burnt in cars, some of the fuel is not completely burnt because of the lack of oxygen

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15
Q

why is carbon monoxide dangerous?

A

carbon monoxide produced can pass out through the exhaust pipe of a car into the atmosphere. It is dangerous as it is poisonous to humans as it reduces the capacity of the blood to carry oxygen

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16
Q

how are nitrogen oxides formed in car engines?

A

the temperature in a car engine is high enough for nitrogen and oxygen from the air to react to form oxides of nitrogen. The oxides pass out through the exhaust of the car and when they get into the atmosphere, they can dissolve in the water in the air to form acid rain

17
Q

what are the problems caused by acid rain?

A
  • acid rain reacts with metals and rocks such as limestone, causing damage to buildings and statues
  • damages the waxy layers on the leaves of trees making it more difficult for trees to absorb minerals
  • make rivers and lakes too acidic for aquatic life to survive
18
Q

what is the experimental technique for the separation of mixture?

A

fractional distillation- to separate two or more liquids that are miscible with each other. eg. ethanol and water

19
Q

what does miscible mean?

A

forming a homogenous mixture when added together

20
Q

how does fractional distillation of crude oil produce more long-chain hydrocarbons that can be used directly and fewer short-chain hydrocarbons than required?

A
  • long- chain hydrocarbons are less flammable and more viscous
  • short-chain hydrocarbons burn well and flow well
  • long chain hydrocarbons can be cracked which breaks them up into short-chain ones
21
Q

what is a homologous series?

A

compounds in the same homologous series have the same general formula and similar chemical properties

22
Q

what is a hydrocarbon?

A

a hydrocarbon is a compound made up only of hydrogen and carbon atoms

23
Q

what does the term saturated mean?

A

saturated means something has bonded as many times as possible.

24
Q

what does the term unsaturated mean?

A

unsaturated means more bonds can be made

25
Q

what does the term ‘genera formula’ mean?

A

general formula is the most simplified the ratio of molecules can be

26
Q

what does the term isomerism mean?

A

isomers have the same general formula but different structures

27
Q

what is the general formula of alkanes?

A

alkanes is a homologous series with the formula CnH2n+2. What this means is that for every one carbon there are two times the amount of hydrogens plus two more hydrogens

28
Q

describe the substitution reaction of methane with bromine to from bromomethane (UV light)

A

In UV light bromine and methane will form bromomethane:
CH4+Br2=CH3Br+HBr
what has happened in this reaction is a bromine has taken the place of a hydrogen (substitution)

29
Q

describe the dehydration of ethanol to ethene?

A

C2H5OH=C2H4+H20
ethanol=ethene+water
Aluminium oxide is the catalyst for this reaction
Alcohols all contain the -OH group and this is generally responsible for their chemical properties and reactions

30
Q

what is the order in the fractionating column?

A
  • refinary gas
  • petrol
  • naptha
  • kerosene
  • diesel
  • lubricating oil
  • fuel oil
  • bitumen
31
Q

why is cracking necessary?

A

less useful longer-chain (alkanes) are converted into more useful shorter-chain alkanes

32
Q

what are uses of poly(ethene)?

A
  • making plastic bags

- plastic bottles

33
Q

what are uses of poly(propene)?

A
  • rope

- crates

34
Q

why are polymers hard to dispose of?

A

Most addition polymers are inert. All this means is that they do not react easily (due to the fact that the carbon bonds are very strong and hard to break). This means that it takes a really long time for addition polymers to biodegrade. Furthermore, burning plastics releases toxic chemicals so that’s not a good idea either. Because of this, it is hard to dispose of polymers (that’s why we recycle them).

35
Q

what are the names of the first 4 alkanes?

A
  1. methane
  2. ethane
  3. propane
  4. butane
36
Q

what are the names of the first 4 alkenes?

A
  1. ethene
  2. propene
  3. butene
  4. pentene

IGCSE Chemistry- Part 3 (2 decks)

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