4.5 Organic 1

Question 1

fractional distillation stages

Answer 1

1. add in the heated oil (already vaporized)
2. vapours rise and condense when cool enough
3. different vapours condense at different heights
4. similar hydrocarbons condense together (because they have similar boiling points)

Question 2

what is crude oil

Answer 2

a mixture of hydrocarbons

Question 3

what is the order of fractions (top to bottom) and their uses

Answer 3

refinery gases - fuel for cooking
gasoline- fuel for cars
kerosene - fuel for aircraft
diesel - fuel for trains
fuel oil - fuel for ships
bitumen - making roads

(viscosity increases and colour gets darker)

Question 4

names of the first 5 alkanes

Answer 4

1 - CH4 - Methane
2 - C2H6 - Ethane
3 - C3H8 - Propane
4 - C4H10 - Butane
5 - C5H12 - Pentane

… next are named after shapes - hexane, heptane, octane etc.

Question 5

what are alkanes

Answer 5

hydrocarbons that fit the general formula CnH2n+2

Question 6

Displayed formula

Answer 6

diagram showing the positions of every atom and every bond

Question 7

Structural formula

Answer 7

Shows the structure in one line, read from left to right like a word
e.g. CH3CH2CH2CH3

Question 8

Molecular formula

Answer 8

shows how many carbon and hydrogen atoms there are
e.g. C4H10

Question 9

Empirical formula

Answer 9

shows the simplest whole-number ratio of carbon to hydrogen
e.g. C2H5

Question 10

homologous series

Answer 10

a family of molecules which has:
- similar chemical reactions
- trends in physical properties
- same general formula

Question 11

isomers definition

Answer 11

molecules with the same molecular formula but different structural formula - think of it as a piece of string when drawing - cannot just bend it, must change it

Question 12

general formula of alkanes

Answer 12

CnH2n+2

Question 13

general formula of alkenes

Answer 13

CnH2n

Question 14

Displayed formula of alkanes

Answer 14

all single carbon bonds

Question 15

Displayed formula of alkenes

Answer 15

one carbon double bond

Question 16

Saturated or unsaturated?

Answer 16

alkanes - saturated
alkenes - unsaturated

Question 17

type of reaction with bromine

Answer 17

alkanes - substitution
alkenes - addition

Question 18

complete combustion of alkanes

Answer 18

occurs when there is excess oxygen
produces carbon dioxide and water only

Question 19

incomplete combustion of alkanes

Answer 19

not enough oxygen
produces carbon monoxide and soot
lowers oxygen capacity of blood and causes lung diseases

Question 20

what does combustion of alkanes as fuels release (significant pollutants) into the atmosphere

Answer 20

carbon dioxide - greenhouse gas, causes climate change

nitrous oxides - dissolves in rainwater forming acid rain

sulphur dioxide - dissolves in rainwater forming acid rain

Question 21

what are most alkanes used for

Answer 21

as fuels because they release a lot of energy when combusted

Question 22

alkanes reacting with halogens

Answer 22

alkanes react with halogens by swapping one hydrogen atom for one halogen atom

it is a substitution reaction
needs UV light as the alkane is pretty unreactive

Question 23

what is cracking

Answer 23

breaking down longer alkanes into smaller, more useful ones (shorter ones are much more useful)

Question 24

cracking conditions

Answer 24

temperature: 650 degrees
catalyst: silica (can be done without a catalyst but far more energy would need to be provided)

Question 25

products of cracking

Answer 25

long alkane --> shorter alkane + alkene

Question 26

name the first 4 alkenes

Answer 26

2 - C2H4 - Ethene 3 - C3H6 - Propene 4 - C4H8 - Butene 5 - C5H10 - Pentene

Question 27

what are alkenes

Answer 27

hydrocarbons that fit the general formula CnH2n

Question 28

differences between alkanes and alkenes

Answer 28

alkenes have a double bond alkenes are unsaturated, alkanes are saturated

Question 29

combustion/incomplete combustion of alkenes

Answer 29

same as alkanes

Question 30

alkene reaction with bromine

Answer 30

they break the double bond and join onto the carbons where the double bond was addition - adding bromine atoms no UV light - more reactive than alkanes turns from orange to colourless

Question 31

formation of addition polymers

Answer 31

when molecules with a carbon double bond add into chains the small molecules that add together are called monomers the long chain they form are called polymers (to draw, break the double bond, add brackets with a line crossing each one and write n outside)

Question 32

disposal issues of addition polymers

Answer 32

they are inert - very unreactive so don't break down easily options to break them down are: reuse recycle incinerate landfill