paper 2 organic chemistry

Question 1

how crude oil is formed

Answer 1

formed over millions of years from the remains of plankton

mixture of hydrocarbons

Question 2

what are hydrocarbons

Answer 2

molecules made up of only hydrogen and carbon atoms only

Question 3

general formula of alkanes

Answer 3

CnH2n + 2

Question 4

why are alkanes saturated molecules

Answer 4

saturated molecules as the carbon atoms are fully bonded to hydrogen atoms

Question 5

viscosity of hydrocarbons

Answer 5

tells us the thickness of a fluid

fluids with high viscosity flow slowly

long chain hydrocarbons are extremely viscous

Question 6

flammability of hydrocarbons

Answer 6

how easily a hydrocarbon combusts

short chain hydrocarbons are extremely flammable

as the size of the hydrocarbon increases the flammability decreases

Question 7

boiling point of hydrocarbons

Answer 7

short chain hydrocarbons have low boiling points

as the size of the hydrocarbons increase the boiling point increases

Question 8

combustion of hydrocarbons

Answer 8

hydrocarbon fuels release enrgy when combusted

during combustion the hydrogen and carbon atoms react with oxygen- they are oxidised

if the oxygen is unlimited then the reacction produces carbon dioxide and water

this is called complete combustion

Question 9

fractional distillation of crude oil

Answer 9

firstly, the crude oil is heated to a very high temperature which causes the crude oil to boil- all the hydrocarbons evaporate and turn into a gas

the crude oil vapour is fed into the fractional distillation column- the column is hotter at the bottom and cooler at the top

hydrocarbon vapours now rise up the vapour - hydrocarbons condense when they reach their boiling point

the liquid fractions are removed

the remaining hydrocarbons continue moving up the column
these now condense when they reach their boiling points

very long chain hydrocarbons have very high boiling points - these hydrocarbons are removed from the bottom of the column

very short chain hydrocarbons have very low boiling points and these do not condense- they are removed from the top of the column as gases

Question 10

cracking

Answer 10

a large alkane is broken down to produce smaller more useful ones

Question 11

types of cracking

Answer 11

catalytic cracking- use heat and a catalyst
the catalyst speeds up the reaction

steam cracking - use heat and steam

Question 12

alkenes

Answer 12

have atleast one double bond
unsaturated molecules - they have 2 fewer hydrogen atoms than alkane with the same number of carbon atoms
more reactive than alkanes

Question 13

how to test for alkenes

Answer 13

using bromine water

if we shake our alkene with bromine water , the bromine water turns from orange to colourless

Question 14

alkene formula

Answer 14

CnH2n

Question 15

what does functional group mean

Answer 15

the part of a molecule that determines how it reacts

Question 16

hydrogenation

Answer 16

reacting an alkene with hydrogen produces an alkane

Question 17

reaction of alkenes with water (hydration)

Answer 17

water must be in the form of steam
temp must be around 300 degrees
the pressure must be around 70 atmospheres
phosphoric acid is used as a catalyst

reversible reaction

Question 18

reaction of alkenes with halogens

Answer 18

alkenes react rapidly with halogens

Question 19

alcohol functional group

Answer 19

OH