7a:hydrocarbons and crude oil

Question 1

what is a hydrocarbon?

Answer 1

compound containing only hydrogen and carbon

Question 2

what are the simplest type of hydrocarbons?

Answer 2

alkanes

Question 3

how many bonds do carbon atoms and hydrogen form in alkanes?

Answer 3

carbon form four bonds and hydrogen form one bond

Question 4

what does saturated mean?

Answer 4

no carbon-carbon double bonds

Question 5

what is the general formula of alkanes?

Answer 5

C ₙH₂ₙ₊₂

Question 6

what do the properties of hydrocarbons depend on?

Answer 6

depends on how long the carbon chain is

Question 7

what are first four alkanes?

Answer 7

methane
ethane
propane
butane

Question 8

how does the size of the alkanes affect their properties?[4]

Answer 8

1. small alkanes have lower boiling points
2. small alkanes are more flammable
3. small alkanes have cleaner flames which aren’t as smoky as larger carbons
4. small alkanes are less viscous(so more runny)

Question 9

the equation of complete combustion of hydrocarbons?

Answer 9

hydrocarbon+oxygen→carbon dioxide+water vapour

Question 10

what happens during the combustion of hydrocarbon fuels?

Answer 10

energy is released and the carbon and hydrogen in the fuels are oxidised

Question 11

what is crude oil?

Answer 11

a mixture of many different compounds,most of the compounds being hydrocarbon molecules(most of the hydrocarbon molecules being alkanes)

Question 12

what is crude oil formed from?

Answer 12

remains of ancient biomass (mainly plankton) that was buried in mud which over millions of years turned to crude oil because of pressure and high temperature

Question 13

how can crude oil be split into separate hydrocarbon groups?

Answer 13

through fractional distillation

Question 14

what can the fractions that were separated through fractional distillation be used for?

Answer 14

can be processed to produce fuels and feedstock for the petrochemical industry

Question 15

how is fractional distillation used to separate crude oils into fractions?[5]

Answer 15

1. crude oil pumped into a fractionating column with a temperature gradient running through it(hot at bottom to cold at top)
2. the crude oil is first heated so that evaporates
3. it is then pumped in at the bottom of the column
4. the gas rises up the column and gradually cools
5. different compounds have different boiling points and therefore condense at different levels in the fractionating column

Question 16

what are alkanes?

Answer 16

saturated hydrocarbons

Question 17

what fuels can be made from the fractions from crude oil?

Answer 17

diesel oil,petrol,kerosene,heavy fuel oil and LPG which are important to modern life

Question 18

what is the feedstock used by the petrochemical industry used for?

Answer 18

to make new compounds for use in things like polymers,solvents,lubricants and detergents

Question 19

what does the uses if hydrocarbons depend on?

Answer 19

their properties

Question 20

what are organic compounds?

Answer 20

compounds containing carbon atoms

Question 21

are the products you get from crude oil organic compounds?

Answer 21

yes

Question 22

why are there such a large variety of products/carbon compounds?

Answer 22

carbon atoms can bond to form similar compounds(homologous series)

Question 23

what is a homologous series?

Answer 23

groups containing similar compounds that all have
1. the same general formula
2. same functional group
3. similar chemical properties

Question 24

why are short-chain hydrocarbons more useful than long-chain hydrocarbons?

Answer 24

short-chain are flammable do they make good fuels and are high in demand however long-chain hydrocarbons form thick liquids which aren’t useful

Question 25

what is cracking?

Answer 25

longer molecules produced from fractional distillation are turned into smaller molebeing broken