ORGANIC CHEMISTRY

Question 1

General formula for alkanes

Answer 1

CnH2n+2

Question 2

are alkanes saturated or unsaturated

Answer 2

staurated compounds

Question 3

Isomers definition

Answer 3

molecules that have the same molecular formula, but different structural formulas, this means they are made of the same atoms, but the atoms are arranged differently

Question 4

homologous series definition

Answer 4

group of organic compounds that have similar chemical properties, due to them having the same functional group.

Question 5

properties of alkanes (trends)

Answer 5

boiling point increases as chain lengthens
shorter = more volatile - evaporate more easily
longer = more viscous
shorter = more flammable

Question 6

main uses of hydrocarbons

Answer 6

FUEL - release loads of energy in combustion

Question 7

equation for complete combustion

Answer 7

hyrdrocarbon + oxygen —–> carbon dioxide + water

Question 8

is combustion an exo or endotheric reaction

Answer 8

exo - releases LOADS of energy

Question 9

what does combustion always produce

Answer 9

carbon dioxide and water

Question 10

properties of short chain alkanes

Answer 10

low boiling point
less viscous
more volatile
more flammable

Question 11

when does complete combustion take place

Answer 11

only if theres enough oxygen

Question 12

what is it called when alkanes are used as fuels

Answer 12

combustion

Question 13

properties of long chain alkanes

Answer 13

less volatile
higher boiling point
less flammable
more viscous

Question 14

During a combustion reaction, are carbon and hydrogen oxidised or reduced?

Answer 14

oxidised

Question 15

is crude oil a finite resource

Answer 15

yes

Question 16

what is crude oil

Answer 16

mixture of many different compounds - most of the compounds are hydrocarbons

Question 17

how was crude oil made

Answer 17

1. formed from the remains of dead plants & animals, particularly plankton
2. these remains were covered by mud & sand , and buried in the earth
3. over millions of years these organic remains were compressed under a lot of heat & pressure
4. the heat and pressure chemically changed the organic remains into crude oil

Question 18

how does fractional distillation work

Answer 18

heat crude oil to v high temp so all compounds are evaporated from liquid to gas
the hot gaseous hydrocarbons rise up the fractionating columns
as they rise they cool down as the top of the column is cooler than the bottom
the hydrocarbons will condense when they become cooler than their boiling point , and the liquid hydrocarbons then collect in trays and drain out
the longer chain hydrocarbons condense at the bottom of the column as they have high boiiling points
the short chain hydrocarbons consense at the top as they have lower boiling points

Question 19

is the fractionating column cooler at top or bottom

Answer 19

top

Question 20

what is feedstock

Answer 20

raw material used to provide reactants for an industrial reaction

( all the diff hydrocarbons in crude oil are feedstocks)

Question 21

what is a petrochemical

Answer 21

a substance made from crude oil, via chemical reactions

Question 22

equation for alkane cracking

Answer 22

long chain alkane ————> shorter alkane +alkene

Question 23

are alkenes unsaturated or saturated

Answer 23

unsaturated (has double bond)

Question 24

test for alkenes

Answer 24

turns bromine water colourless

Question 25

is alkene or alkane more reactive

Answer 25

alkene

Question 26

how can polymers be formed from alkenes

Answer 26

double bond breaks to from two or more bonds

Question 27

what is cracking

Answer 27

the process of splitting longer chain hydrocarbons into shorter chain hydrocarbons

Question 28

whatv type of reaction of cracking

Answer 28

thermal decomposition

Question 29

catalytic cracking method

Answer 29

1. long chain alkanes are heated until they vapourise 2. then theyre passed over a hot powedered aluminium oxide catalyst (pourous pot) 3.this brekas the long chain alkanes into a short chain alkane and an alkene

Question 30

how is steam cracking different to catalytic

Answer 30

no catalyst involved instead the long chain alkane is mixed w steam at vvvvv high temps

Question 31

what does cracking always produce

Answer 31

ALKANE AND ALKENE

Question 32

formula for alkenes

Answer 32

CnH2n