p4. organic chemistry

Question 1

what is crude oil?

Answer 1

• finite resource found in rocks
• remains found in ancient biomass mainly containing plankton
• mixture of large numbers of compounds
• mostly hydrocarbons ( hydrogen and carbon atoms ) = alkanes

Question 2

list uses of crude oil

Answer 2

• fuels = petrol,diesel and heavy fuel oil
• feedstock for petrochemical industry

Question 3

list four alkanes

Answer 3

• methane
• ethane
• propane
• butane

Question 4

describe process of fractional distillation

Answer 4

• heated crude oil enters tall fractionating column = hot at the bottom,cold at the top
• vapour through oil rises through column
• vapour condenses when its cool enough
• liquids let out at different heights of column

Question 5

purpose of fractional distillation

Answer 5

• separate crude oil into more simple and useful mixtures
• can be used as different hydrocarbons have different melting points

Question 6

difference between weak intermolecular forces and strong intermolecular forces

Answer 6

• weak = low boiling points
  ~ dont condense
  ~ leave column as a gas
• strong = high bowling points
  ~leave column as hot liquid

Question 7

properties of the gas fractions which contain hydrocarbons with one to four carbon atoms

Answer 7

• boiling points below room temperature
• very flammable
• low viscosity

Question 8

properties of the gas fractions which contain hydrocarbons with 35 or more carbon atoms

Answer 8

• boiling points well above room temperature
• difficult to ignite
• high viscosity

Question 9

trend in properties of hydrocarbons

Answer 9

• boiling points
• flammability
• viscosity

Question 10

what is complete combustion

Answer 10

• occurs when there is a good supply of air
• carbon and hydrogen atoms in fuel react with oxygen in an exothermic reaction
• carbon dioxide and water are produced
• maximum amount of energy given out

Question 11

what is cracking

Answer 11

• process of hydrocarbons being broken down into more simple and useful molecules

Question 12

what is catalytic cracking

Answer 12

• heating hydrocarbon to 470-550 to vaporise
• vapour then passes over hot powdered catalyst of aluminium oxide

Question 13

what is steam cracking

Answer 13

• heating is higher ( 850 )
• produces more ring structures and unsaturated compounds
• no catalyst used

Question 14

difference between alkanes and alkenes

Answer 14

• alkanes = saturated and joined by singular C-C bonds
• alkenes = unsaturated and contain at least one double C=C bond
  ~ more reactive than alkanes
  ~ take part in reactions that alkanes cannot