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AQA GCSE - Chemistry - paper 2 > Organic chemistry > Flashcards

Organic chemistry Flashcards

1
Q

What is a hydrocarbon?

A

A hydrocarbon is any compound that is formed from carbon and hydrogen atoms only.

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2
Q

Describe an alkane:

A
  • all have C-C bonds
  • part of the homologous series
  • saturated compounds, each carbon has made 4 bonds
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3
Q

what is the mnemonic to remember the first four alkanes?

A

Monkeys - Methane
Eat - Ethane
Pealed - Propane
Bananas - Butane

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4
Q

How do hydrocarbon properties change as the chain gets longer?

A
  • it becomes more viscous (thicker)
  • it becomes less volatile (higher boiling point)
  • it becomes less flammable (harder to ignite)
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5
Q

What is the word equation for complete combustion (oxygen is in excess)

A

hydrocarbon + oxygen –> carbon dioxide + water

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6
Q

What is crude oil?

A

Crude oil is a fossil fuel. It is a finite resources so it will run out.

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7
Q

What is fractional distillation?

A

1) The oil is heated until most of it has turned into gas. The gases enter a fractionating column (and the liquid is drained off)
2) In the column there is a temperature gradient (it is hot at the bottom and gets cooler as you move up)
3) The longer hydrocarbons have high boiling points. They condense back into liquids and drain of the column early on, near the bottom. The shorter hydrocarbons have lower boiling points so they condense and drain further up the column.
4) You end up with the oil separated into different fractions. Each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms (so similar boiling points)

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8
Q

What is crude oil used for in modern life?

A
  • fuel for most modern transport
  • feedstock to make new compounds
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9
Q

What is cracking?

A

Cracking is splitting up long-chain hydrocarbons, it is a thermal decomposition reaction:
1) heat long-chain hydrocarbons to vaporise them
2) then the vapour is passed over a hot powdered catalyst - aluminium oxide
3) the long-chain molecules split apart on the surface of the catalyst - catalytic cracking
4) you can also crack hydrocarbons if you vaporise them, mix with steam and heat them to a high temperature - steam cracking

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10
Q

What are alkenes?

A
  • alkenes are hydrocarbons with a double bond between two carbon atoms in the chain
  • ## the C=C bond means they have two fewer hydrogens compared to alkanes - they are unsaturated
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11
Q

what are the first four alkenes?

A

Ethene, propene, butene, pentene

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12
Q

What is the general formula for alkenes?

A

CnH2n

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13
Q

What is the general formula for alkanes?

A

CnH2n+2

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14
Q

What is the word equation for incomplete combustion?

A

alkene + oxygen –> carbon + carbon monoxide + water

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15
Q

How do alkenes react?

A

Alkenes react via addition reactions - the double bond means that it can be split, making it possible to add a new atom

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16
Q

What is a functional group?

A

A group of atoms in a molecule that determine how that molecule typically reacts/

17
Q

What is hydrogenation?

A
  • this is the addition of hydrogen
  • hydrogen can react with the double bonded carbons to open the double bond and form a saturated alkane/ You need to have a catalyst
18
Q

How are alcohols formed?

A
  • reacting steam with alkenes forms alcohols
  • When alkenes react with steam, water is added across the double bond and an alcohol is formed
19
Q

How do halogens react with alkenes?

A
  • Alkenes will also react in addition reactions with halogens like bromine, chlorine and iodine
  • The molecules formed are saturated, with the C=C becoming bonded to a halogen atom
20
Q

what are polymers?

A

Polymers are long molecules formed when lots of small molecules (monomers) are joined together. This reaction is called polymerisation

21
Q

Explain addition polymers:

A
  • the monomers that make up addition polymers have a double covalent bond
  • lots of unsaturated monomer molecules (alkenes) can open up their double bonds and join together to form polymer chains; addition polymerisation
  • When the monomers react in addition polymerisation reactions, the only product is the polymer, so an addition polymer contains the same type and number of atoms as the monomer that formed it
22
Q

How to draw the repeating unit of a polymer?

A

1) draw the two alkene carbons, replacing the double bond with a single bond and add an extra single bond to each of the carbons
2) then fill in the rest of the groups in the same way that they surrounded the double bond in the monomer
3) draw brackets around the repeating part (make sure the sticks go through the bracket), and put an “n” after it

23
Q

How to get the displayed formula of a polymer?

A

1) draw out the repeating part of the polymer, and get rid of the two bonds going out through brackets. put a double bond between carbons
2) The name of the polymer is the alkene with “poly” written before it

24
Q

Describe the alcohol group:

A
  • functional group “-OH”
    -the name will end in “-ol”
  • the general formula is: CnH2n+1-OH
  • they all have similar properties
25
Q

Describe the alcohol group properties:

A
  • flammable
  • they undergo complete combustion
  • the first four are all soluble in water, their solutions have a neutral pH
  • they react with sodium
  • alcohols can be oxidised by reacting with oxygen
  • different alcohols form different carboxylic acids
26
Q

What are alcohols used for?

A
  • they are used as solvents as they can dissolve most of what water can dissolve, as well as things water cannot dissolve
  • the first four are used as fuels as they burn fairly cleanly and non-smelly
27
Q

how is ethanol made through fermentation?

A

__________yeast_____________________________
sugar ————> ethanol + carbon dioxide

28
Q

Describe the carboxylic acids:

A
  • functional group “-COOH”
  • they are part of the homologous series
  • their names end in “-anoic acid”
29
Q

Describe the carboxylic acids properties?

A
  • they react like all other acids, with carbonates to produce a salt, water and carbon dioxides
  • the salts formed in these reactions and end in “-aoate”
  • carboxylic acids can dissolve in water. When they dissolve, they ionise and release H+ ions, resulting in an acidic solution
30
Q

How are esters made from carboxylic acids?

A
  • esters have the functional group “-COO-“
  • esters are formed from an alcohol and a carboxylic acid
  • an acid catalyst is often used (like sulfuric acid)
  • the formula is:
    alcohol + carboxylic acid ——> ester + water
31
Q

What is condensation polymerisation?

A
  • it involves monomers which contain different functional groups
  • the monomers react together and bonds form between them, making polymer chains
  • for each new bond that forms, a small molecule is lost. This is why its called condensation polymerisation
  • The simplest types of condensation polymers contain 2 different types of monomer, with two of the same functional group
32
Q

describe addition polymerisation VS condensation polymerisation:

A

Number of type of monomers:
A - only one monomer type containing C=C
C - two monomer types each containing two of the same functional groups OR one monomer type with 2 different functional groups
number of products:
A - only one product formed
C - two types of product - the polymer and a small molecule
functional groups involved in polymerisation:
A - carbon-carbon double bond in monomer
C - two reactive groups on each monomer

33
Q

How are amino acids naturally occurring polymers?

A
  • they have an amino group (NH2) and an acidic carboxyl group (COOH)
34
Q

Why are proteins polymers of amino acids?

A
  • amino acids can form polymers known as polypeptides via condensation polymerisation
  • the amino group can react with the acid group to form a chain. For every new bond that is formed a molecule of water is lost
  • One or more long-chains of polypeptides make proteins.
35
Q

How is DNA molecules made from nucleotide polymers?

A
  • DNA is made of 2 polymer chains of monomers - nucleotides. the nucleotides each contain a small molecule known as a “base”
  • There are 4 bases (A,C,G,T)
  • The bases on the different polymer chains pair up with each other and form cross links keeping the two strands of nucleotides together and giving the double helix structure
  • the order of the bases acts as a code for an organism’s genes
36
Q

How do simple sugars form polymers?

A

Sugars are small molecules that contain; carbon, oxygen, hydrogen. Sugars can react together through polymerisation reactions to form larger carbohydrate polymers, which living things use to store energy, and cellulose, which is found in plant cell walls

AQA GCSE - Chemistry - paper 2 (5 decks)

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