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chemistry > Topic 7 - organic chemistry > Flashcards

Topic 7 - organic chemistry Flashcards

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1
Q

what is a hydrocarbon

A

a compound that contains ONLY hydrogen and carbon

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2
Q

what is an alkane and what is the general formula for one

A

the simplest type of hydrocarbon
C n H2n+2

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3
Q

what type of series are alkanes and what does this mean

A

homologous series
a group of organic compounds that react in a similar way

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4
Q

are alkanes saturated or unsaturated

A

saturated compounds
each carbon atom forms four single covalent bonds

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5
Q

what are the first four alkanes

A

methane
ethane
propane
butane

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6
Q

how do hydrocarbon properties change as the chain gets longer

A

the shorter the carbon chain , the more runny a hydrocarbon is - the less viscous it is .
hydrocarbons with shorter carbon chains are also more volatile i.e. they have lower boiling points
also , the shorter the carbon chain, the more flammabble the hydrocarbon is.
the properties of hydrocarbons affect how they are used for fuels. showrt chains are used as bottled gases stored under pressure as liquids in bottles.

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7
Q

what is the formula for the complete combustion of a hydrocarbon

A

hydrocarbon + oxygen -> carbon dioxide + water + energy

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8
Q

what are hydrocarbons used for and why

A

fuel as they re;easea huge amount of energy when they combust completely

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9
Q

during combustion are caarbon and hydrogen from the hydrocarbon reduced or oxidised

A

oxidised

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10
Q

what is crude oil and how is it made

A

crude oil is a fossil fuel
it is formed from the remains of plants and animals mainly plankton, that died millions of years ago and were buried in the mud. over millions of years, with high temperature and pressure, the remains turn to crude oil which can be drilled up from the rocks where it is found.

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11
Q

how is crude oil seperated and why

A

crude oil is a mixture of lots of hydrocdarbons .
these different compounds are seperated using fractional distillation

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12
Q

explain how fractional distillation works

A

the oil is heated up untill most of it has turned to gas. the gases enter a fractionatinf collumn .
In the collumn there is a temperatue gradient . hot at the bottom and cooler at the top.
the longer hydrocarbons have high boiling points. they condense back to liquid and drain out of the collumn early on, when they are near the bottom. the chorter hydrocarbons have lower boiling points. they condense and drain out much later on near to the top of the collum where it is cooler.
you end up with the crude oil mixture seperated out into different fraction . each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms .so have similar boiling points .

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13
Q

what do we use crude oil for

A

oil provides fuel for most modern transport - cars, trains, planes.
diesel oil , kerosene , heavy fuel oil and LPG (liquid petroleum gas ) all come from crude oil

the petrochemical industry uses some of the hydrocarbons from crude oil as a feedstock to make new compounds for use in things like polymers solvents lubricants and detergents.

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14
Q

why is there a large variety of products from crude oil

A

carbon atoms can form together to form different groups called homologous series .

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15
Q

why do we use cracking

A

short chain hydrocarbons are flammable so make good fuels and are in high demand.
however, long chain hydrocarbons form thick gloopy liquids like tar which arent usefull so a lot of the longer alkane molecules produced from frational distillation are turned into smaller more usefull ones by a process called cracking.

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16
Q

what does cracking produce and how are they useful

A

alkenes , used as a starting material when making lots of other compounds and can be used to make polymers.
some of the products of cracking are useful as fuels e.e.g petrol for cars and paraffin for jet fuel

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17
Q

explain how cracking works

A

cracking is a thermal decomposition reaction - breaking molecules down by heating them .
the first step is to heat long chain hydrocarbons to vaporise them .
then the vapour is passed over a hot powdered aluminium oxide catalyst.
the long chain molecules split apart on the surface of the speck of catalyst. this is catalytic cracking.
you can also crack hydrocarbons if you vaporise them, mix them with steam and then heat them to a very high temperature. this is known as steam crakcing

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18
Q

what are alkenes

A

hydrocarbons with a double bond between two of the carbon atoms in their chain .
the c=c double bond means that alkenes have two fewer hydrogens compared with alkanes containing the same number of carbon atoms

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19
Q

are alkenes saturated or unsaturated and what is its general formula

A

unsaturated
CnH2n

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20
Q

what makes alkenes reactive

A

the c=cdouble bond can open up to make a single bond allowing the two carbon atom s to bond with other atoms .

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21
Q

what are the first four alkenes

A

methene
ethene
propene
butene

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22
Q

why can’t alkenes carry out complete combustion

A

in large amounts of oxygen they combust completely to produce only water and co2.
however there isnt enough oxygen in the air for this.

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23
Q

what is the word equation for the incomplete combustion of an alkene

A

alkene + oxygen -> carbon + carbon monoxide + carbon dioxide + water + energy

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24
Q

what is the issue with incomplete combustion of an alkene

A

produces carbon monoxide which is a poisonous gas
produces smoky yellow flame and less energy

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25
Q

what is a functional group

A

a group of atoms in a molecule that determine how that molecule typically reacts .

26
Q

what is the functional group of an alkene

A

c=c

27
Q

most of the time how will alkenes react

A

via addition reactions where the carbon carbon douvle bond will open up to leave a single bond and a new atom is added to each carbon

28
Q

what is hydrogenation

A

where hydrogen can react withthe double bonded carbon to open up the double bond and form the equivalent unsaturated alkane
the alkene is reacted with hydrogen in the presence of a catalyst

29
Q

how can alkenes produce alcohols

A

when alkenes react with steam , water is added across the double bond and an alcohol is formed.
e.g. ethanol can be made by micing ethene with steam and then passing it over a catalyst.
this conversion of ethene to ethanol is one way of making ehtanol industrially.
after the reaction has taken place. the reaction mixture is passed from the reactor into a condenser . ethanol and water have a higher boiling point than ethen so both condense whilst any unreacted ethene gas is recyled back into the reactor. the alcohol can then be purified from the mixture by fractional distillation

30
Q

how do halogens react with alkenes

A

alkenes will react in addition reactions with halogens suchas vromine chlorine and iodine.
the molecules formed are saturated, with teh c=c carbons each becoming bonded to a halogen atom.
e.g. bromine and ethene react together to form dibromoethane

31
Q

how can the addition of bromine to a double bond be used to test for alkenes

A

when orange bromine water is added to a saturated compound, like an alkane , no reaction will happen and it will stay bright orange.
if it is added to an alkene the bromine will add across the double bond making a colourless dibromo compound so the bromine water is decolourised

32
Q

what are polymers

A

long molecules formed when lots of small molecules called monomers join together. this reaction is called polymerisation and it usually needs high pressure and a catalyst.
plastics are made up of polymers and are usually carbon based and their monomers are often alkenes

33
Q

what is addition polymerisation

A

the monomers that make up addition polymers have a double covalent bond.
lots of unsaturated monomer molecules can open up their double bonds and join together to form polymer chains. this is called addition polymerisation
the addition polymer contains exactly the same type and number of atoms as the monomers that formed it .

34
Q

how do you draw the displayed formula of an addition polymer from the displayed formula of its monomer

A

start by drawing the two alkene carbons. replace the double bond with a single bond and add an extra single bond to each of the carbons.
then fill the rest of of the groups in the same way that they suround the double bond in the monomer . finnaly , stick a pair of brackets around the repeatung bit and put an n after it to show there are lots of monomers

35
Q

how do you name a polymer

A

the name comes from the type of monomer its made from so you just put the word poly in front of it and put the monomer name in brackets e.g. propene becomes poly(propene)

36
Q

what is the general formula of an alcohol

A

Cn H2n+1OH

37
Q

what is the functional group of alcohols

A

-OH

38
Q

what are the first four alcohols in the homologous series

A

methanol
ethanol
propanol
butanol

39
Q

do alcohols carry out complete or incomplete comnbustion in air and what is the equation for this

A

complete
alcohol + oxygen -> carbon dioxide +water

40
Q

what are the properties of the first four alcohols

A

soluble in water
neutral ph
react with sodium
can be oxidised by reacting with oxygen to produce a carboxylic acid

41
Q

what can the first four alcohols be used for

A

methanol and ehtanol used as solvents in industry as they can dissolve most things water can and can also dissolve substances water cannot. e.g. hydrocarbons oils and fats
used as fuels . e.g. ethanol used as a fuel in spirit burners , it burns fairly cleanly and is non smelly

42
Q

what is the equation for the production of ethanol

A

sugar + yeast -> ethanol + carbon dioxide

43
Q

in what conditions does fermentation work the best

A

temp around 37
slightly acidic
anaerobic conditions

44
Q

what are carboxylic acids

A

a homologous series of compounds that all have -COOH as a functional group
their names end in -anoic acid

it has a c=o double bond

45
Q

how do carboxylic acids react

A

like any other acid with carbonates to produce salt , water and carbon dioxidel
the salts formed in these reactions end in anoate

carboxylic acids can dissolve in water , when they dissolve they ionise and release H+ ions resulting in an acidic solution. but because they ont ionise compoletely, they just form weak acidic solutions, this means that they have a higher PH than aqueous solutions of strong acidswith the same concentration

46
Q

what are esters formed from

A

an alcohol and a carboxylic acid
an acid catalyst is usually used

47
Q

what is the functional group of an ester

A

-COO-

48
Q

what is the word equation for the formation of an ester

A

alcohol + carboxylic acid -> ester + water

49
Q

what does ethanoic acid and ethano lmake

A

ethyl ethanoate and water

50
Q

what is condensation polymerisation

A

involves monomers which contain different functional groups
the monomers react together and bonds form between them making polymer chains.
for each new bon that forms, a small molecule is lost.
this is why its called condensation polymerisation

51
Q

what are the differences between addition polymerisation and condensation polymerisation

A

addition polymerisation

only one monomer type containing a c=c bond
only one product formed
carbon carbon double bond in monomer

condensation polymerisation

two monomer types each containing two of the same functional group or one monomer type with two different functional types
two types of product - the polymer and a small molecule e.g. water
two reactive groups on each monomer

52
Q

what functional groups does an amino acid have and give an example of an amino acid

A

amino group NH2
acidic carboxyl group COOH

glycine - the smallest and simplest amino acid.

53
Q

what is a polypeptide

A

amino acids form them via condensation polymerisation
the amino group of an amino acid can react with the amino group of another to forma polymer chain . for every new bond that is formed a molecule of water is lost.

54
Q

wjat are long chains of polypeptides known as

A

proteins

55
Q

why are proteins important for us

A

proteins have important uses in the human body
enzymes work as catalysts
haemoglobin transpoets oxygen
antibodies form part of the immune system
the majority of body tissue is made from protein

56
Q

what gives proteins their different properties and shapes

A

the order ofamino acids in the chain

57
Q

what is the structure of DNA

A

double helix structure
made of two polymer chains of monomers called nucleotides.
they each contain a small molecule called a base

58
Q

what are the four different bases in nucleotides and what do they do

A

A
C
G
T
the bases pair up with eachother and form cross links keeping the two strands of nucleotides together and giving the double helix structure.
the order of the bases act as a code for an organimsms genes.

59
Q

what are sugars

A

small molecules that contain carbon, oxygen and hydrogen

60
Q

sugars can react together through polymerisation reactinos to produce what
give examples

A

larger carbohydrate polymers
e.g. starch ,
cellulose

chemistry (7 decks)

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