MODULE 7 - ORGANIC CHEMISTRY QUESTIONS WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE.Buy Quality Materials
Alkanes are ______ compounds and are called a _______
Staurated - each carbin atom forms 4 covalent bonds so hold the maximum amount of hydrogen in its structure
Homologous series ...
Alkanes are ______ compounds and are called a _______
Staurated - each carbin atom forms 4 covalent bonds so hold the maximum amount of
hydrogen in its structure
Homologous series = a group of organic compound that all react in a similar way
Alkane general formula
CnH2n+2
First 6 alkanes
Methane - ch4
Ethane - c2h6
Propane - c3h8
Butane - c4h10
Pentane - c5h12
Hexane - c6h14
How do the properties of hydrocarbons change as carbon chain length increases
- becomes more viscous
- less volatile
- less flammable
What is crude oil
fossil fuel, formed from remains of plants and animals (mainly plankton), that form crude
oil over millions of years under high pressure with high temperatures
Non - renewable
A mixture of lots of different hydrocarbons
How does fractional distillation work?
1) crude oil is vaporised into a gas and Exeter's the fractionating column
2) there is a temperature gradient in the column
3) the longer hydrocarbons have high boiling points so condense back to liquids lower
down the column
Shorter hydrocarbons have much lower boiling points so condense higher up
4) As the gas rises, you get fractions contains hydrocarbons of similar chain length
names of the fractions in crude oil
LPG (3 Cs) petrol (8 Cs) kerosene (15 Cs) diesel oil (20 Cs) heavy fuel oil (40 Cs)
Uses of crude oil
fuel - petrol, kerosene, diesel etc
Petrochemical industry uses some of the hydrocarbons then as feedstock make new
compounds like polymers and solvents
What is cracking?
Long chain hydrocarbons being split into shorter chain, more useful hydrocarbons
Produces alkanes and alkenes
, 2 methods of cracking
Step 1 for both is to heat to high temperature to vaporise them
Catalytic cracking : heated to a height temperature and passed over a catalyst (silicon
dioxide or aluminium oxide)
Steam cracking : mix with steam at high temperature
Alkene general formula
CnH2n
What is an alkene
Have a double carbon bond between two carbon in the chain
Means they are unsaturated
Double bond makes them reactive as can open up the double bond and react with other
atoms
Test for alkenes
bromine water orange-brown to colourless shook
What are isomers
compounds with the same molecular formula but different structures and properties
In alkenes the double carbon bond maybe in a different position
Addition reaction of alkenes with halogens
Halogenation
No catalyst needed
For example the bromine water test
Addition reaction of alkenes with hydrogen
Alkenes react with hydrogen in the presence of a nickel catalyst at 150 degrees Celsius
to form alkanes e.g. C2H4 + H2 ----> C2H6
Used in the manufacturing or margarine, as saturating the c=c bond in oils makes the
more spreadable
Addition reaction of alkenes with steam
Alkenes react with steam to form alcohols. An acid catalyst, such as phosphoric acid,
H3PO4, must be present and the conditions of 300 degrees Celsius and 60 atm
Is reversible
What are addition polymers?
They're made up of many unsaturated monomers with a double covalent bonds joined
together
Alkenes open up their c=c
5 uses of poly(ethene)
Packaging film
Trash and shopping bags
Wire and cable insulation
Plastic bottles
Toys
advantages & disadvantages of polymers
Are resistant to chemical attacks so can be used for storing food, drinks and chemicals
Are not biodegradable- have to be incinerated, recycled (for new products or chemical
feedstock), or thrown into landfill
How is low density poly(ethene) produced?
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