Chem paper 2

Le Chatelier’s principle: If a system at equilibrium is subjected to a change, the system will adjust to counteract that change

Reversible reaction are reactions which can change back or forward depending on the environment

Equilibrium is when the forward and backward reactions occur at exactly the same rate

C7

Crude oil found underground created from buried plankton

consists mostly hydrocarbons

most are alkanes which are made up of single-covalently bonded Carbon atoms surrounded by Hydrogen atoms (alkenes are saturated)

H

|

H -- C -- H

|

H

Methane Ethane C2H6 Propane C3H8 Butane C4H10

CH4

Formula for alkanes

Cn = H2n+2 (always twice as many hydrogens + 2)

Meth= 1

eth=2

Prop=3

But=4

etc (amount of carbons)

Fractional distillation separates up crude oil into different fractions for a specific purpose

This done as different hydrocarbons have different boiling points the higher the boiling point the lower down the fraction the hydrocarbon recondenses and the longer the chain of hydrocarbon. The shorter hydrocarbons condense higher up as it is much cooler at the top

Bitumen never turns to gas as it has such a long chain

Longer chains have higher boiling points as their are stronger intermolecular forces to overcome

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Fractions need to know

number of carbons

3 LPG

8 Petrol

15 Kerosene

20 Diesel oil

40 Heavy fuel oil

Bitumen- Roads

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Complete Combustion fuel+oxygen → carbon dioxide + water

Longer alkanes have higher viscosity

shorter alkanes are more flammable

Polymers are made from alkenes which are hydrocarbons with a carbon double covalent bond

alkenes are unsaturated

you can test for alkenes by adding bromine water which turns colourless if bonded with the alkene as it breaks the double bond in the alkene making it saturated

Cracking

breaking a loner alkane into a shorter alkane and alkene

Catalytic cracking uses a zeolite catalyst at 550°C

Steam cracking uses no catalyst and a higher temperature above 800°C