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chemistry > 7-Hydrocarbons > Flashcards

7-Hydrocarbons Flashcards

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1
Q

Formula for alkenes

A

CnH2n

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2
Q

Formula for alkanes

A

CnH2n+2

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3
Q

Methane

A

CH4

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4
Q

Ethane

A

C2H6

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5
Q

Propane

A

C3H8

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6
Q

Butane

A

C4H10

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7
Q

CH4

A

Methane

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8
Q

C2H6

A

Ethane

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9
Q

C3H8

A

Propane

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10
Q

C4H10

A

Butane

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11
Q

Functional group -coo-

A

Esters

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12
Q

Functional group -cooh

A

Carboxyl group- carboyxilic acid

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13
Q

Functional group -oh

A

Hydroxy(l)- alcohols

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14
Q

Carboxylic acid

A

Weak acids

Functional group -cooh- carboxyl

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15
Q

Esters

A

Orgaic compounds, fruity smell, -coo- functional group

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16
Q

Alcohols

A

Functional group -oh
Used as fuel,
reacts with metals to form metal ethanoate,
soluble in water (decreases as chain size gets greater- becomes less miscible),
oxidise without combustion to form carboxylic acids

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17
Q

Uses of alcohols

A

Methanol-chemical feedstock,
ethanol-alcoholic drinks, fuel, solvent(can dissolve organic and inorganic substances), propanol and butanol-fuel and solvent

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18
Q

Fermentation

A

Produces alcohol, sugar dissolved in water mixed with yeast, air lock needed to allow co2 out but no air in, warm temp 25-35 C, yeast dies when ethanol conc reaches 15%
O2 causes ethanol to oxidise into ethanoic acid- vinegar test

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19
Q

What happens if air is present during fermentation

A

The o2 causes ethanol to oxidise into ethanoic acid- vinegar taste

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20
Q

Crude oil

A
  • Finite resource
  • mixture of hydrocarbons
  • formed over millions of years from once living marine plants/animals
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21
Q

Fractions

A

Mixture of hydrocarbons w/ similar boiling points

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22
Q

As increase in chain length of hydrocarbons

A
  • bp increases
  • volatility decreases
  • viscosity increases
  • flammability decreases
23
Q

Alkenes

A
  • CnH2n
  • unsaturated- contain less hydrogen atoms than alkane w/ same number of carbon atoms
  • contains atleast one double bond
24
Q

Homologous series have

A
  • same general formula
  • successive member differ by CH2 unit
  • gradual variation in physical properties eg. Bp
  • similar chemical properties
25
Q

Alkenes reactions

A
  • v. Reactive due to presence of C=C bond
    • undergoes addition reactions
  • in addition reactions C=C becomes C-C
    • allows other atoms to jioin across C-C
  • in functional group C=C
  • burn (but rarely do so)
    • too valuable or making polymers
    • incomplete combustion w/ small flames
26
Q

Testing for alkenes and alkanes

A
  • mix w/ orange brown bromine water
  • alkane- stays orange
  • alkene- decolours - br-br molecule no longer present, has joined alkene molecule
27
Q

Alkenes + halogens

A

Produce haloalkenes
Eg. Chlorine, bromine, iodine
-usually spontaneous reactions

28
Q

Hydrogenation

A

Alkene + hydrogen = alkane

  • (nickel) catalyst
  • 60-150 C each double bond needs one H2 molecule to hydrogenate
  • staigtenes molecules and incrreases melting points
    • make spreadable margarine
29
Q

Hydration

A

Alkene + water = alcohol

  • temp approx 300 C
  • catalyst
  • requires energy to heat gases to generate high pressure
  • unreacted ethane and steam recycles over catalyst - reversable reaction
30
Q

Addition reactions

A
  • molecule combines w/ another molecule forming one larger molecule + no other products
  • alkanes cannot take part
31
Q

Addition polymerisation

A
  • ethene/alkene monomer
  • poly(alkene) polymer
  • c=c in alkene allows molecules to join yogether to form a single product
32
Q

Combustion of alkenes

A
  • test ethene gas w/ lighted splint
  • alkenes burn with a smokier yellow flme Compared to alkanes
  • alkenes relese less energy per mole in combustion that alkanes
    • alkenes not used as fuels

Complete combustion
Alkene + oxygen = carbon dioxide + water

33
Q

Polymers

A
  • long chain molecuules
    • natural eg. Dna
    • man-made -plastics
  • made by joining together thousands of small identical molecules (monomers)
  • two diff types:
    • condensation
    • addition
34
Q

Addition polymers

A
  • monomers are alkenes

- monomer has a C=C bond but polymers have C-C

35
Q

Fractional distillation

A
  • hydrocarbons in crude oil seperayed. Into fractions
    • each contains molecules with a similar number of carbon atoms
      • by fractional distilation
  • fractions can be processed to produce fuels and feedstock for petrochemical industry
36
Q

Crude oil produces

A
  • petrol
  • diesel oil
  • kerosene
  • heavy fuel oil
  • liquified petroleum gas
37
Q

Petrochemical industry produces useful materials such as.

A
  • solvents
  • lubricants
  • polymers
  • detergents

-vast array of natural and synthertic carbon compounds occur due to ability of carbon atoms to formfamily of similar compunds

38
Q

Properties of polymer depend on

A
  • monomer made from

- condition under joined together

39
Q

Low density poly(ethene)

A
  • very high pressure
  • trace of o2
  • polymer chain branched
    • randomly arranged
  • flexible, unreactive, made into fibres, carrier bgs, bubble wrap
40
Q

High density poly(ethene)

A
  • catayst at 50 C
  • slightly raised pressure
  • less branching
    • line up closer- straigter molecules
  • higher softening tmp, stronger than LD
  • strong, flexible, resitsts shattering, chemical attack
  • plastic, bottles,pipes, bucket
41
Q

Thermosoftening polymers

A
  • melt when heated
  • most do
  • can be recycled
  • dont ahve caovalent bonds between neighboring polymer molecules
    • molecules can move over each other when heated- melts
  • weak intermolecular forces
  • when cools- intermolecluar forces bring polymer molecules back together -polymer hardens again- can be remolded
42
Q

Thermosetting

A
  • dont melt
  • char and burn
  • resistant to much higher temp
  • electrical plugs- dont want to melt
  • cross links- covalent bonds between molecules
43
Q

Condensation polymerisation

A

-monomers dont need C=C
-instead have two diff functional groups
-smaller moolecule (usually water) produced as by product
-eg. Polyester-naturally occur as biologicalpolymer
or -made artificially
-simple polyester
-monomer- as hydroxyl (O-H) groups
-another monomer w/ two carboxylic acid groups (-COOH)
-symbols may be used to represent middle of each monomer
-only funtcional group at end cause reaction to take place

44
Q

Examples of biolgical polymers

A
  • DNA
  • protein
  • starch
  • cellulose
45
Q

DNA

A
  • double helix
    • two polymer chains lined up and twisted around each other
  • four diff types monomers
    • nucleotides (CGAT)
  • sequence of nucleotides along DNA molecule -cofe for gene
46
Q

Protein

A
  • biological polymers inside cells
  • amino acids- monomers
  • eg. Enzymes
  • amino acids
    • atleast two functional groups
      • NH2 and -COOH
  • polymers in cells- polypeptide and protein
  • condensation polymerisation
    • each monomer added, growing polymer chain, water molecule produced
47
Q

Starch and cellulose

A
  • made by plants
  • monomers sugar/glucose molecules
  • starch-storing enegry as complex carbs
  • cellulose- strong cell wall
    • gives plant cells strength
48
Q

Making ethanol

A
  • alcohol in beer and other alcoholic drinks
  • fuel for vehicles on own or mixed with petrol
  • can be produced by
    • fermentation and concentrated with fractional distillation -hydrating ethene0 less green as cracking crude oil
49
Q

Combustion of alcohol

A

Complete
Alcohol+O2 = CO2 +H20

Incomplete
Alcohol +O2=C02 +CO+C+H20

50
Q

Reaction of sodium and alcohol

A

Sodium + ethanol = sodium ethanoate +H2

51
Q

Alcohol solubility with water

A
  • short hydrogen chains (MEP) added to water mix easily to priduce solution
  • solubilty dexreases as length of molecule gets longer -may not mix easily, two distinct layer may be left in container
52
Q

Alcohols oxidise

A

-to prouce carboxylc acids
-oxidising agent (O)
Ethanol + oxidising agent [O] = ethanoic acid + water

53
Q

Catalytc crackng

A

550C

Catalyst

54
Q

Steam cracking

A

Over 800C

No catalyst

chemistry (14 decks)

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