alkanes

Question 1

outline how different fractions are obtained in fractional distillation

Answer 1

-crude oil is vaporised
-the vapour passes into the fractioning coloumn
-the top of the coloumn is cooler and the bottom of the coloums are hotter due to a negative temperature gradient
-fractions are separated by boiling points
-longer hydrogencarbons have higher boiling points so stay at the bottom
-shorter hydrocarbon flow to the top as they have lower boiling points

Question 2

thermal cracking

Answer 2

-conditions are high temp and high pressure
-uses free radical intermediates
-produces a high percentage of alkenes and straight chain alkanes

Question 3

catalytic cracking

Answer 3

-conditions are low temperature and slight pressure
-uses the catalyst ‘zeolite’
-uses carbocation intermediates
-produces mainly motor fuels and aromatic hydrocarbons and cyclo alkanes

Question 4

why do we carry out cracking reactions

Answer 4

-shorter chains are in higher demand
-other products such as alkenes are used to make plastics and polymers

Question 5

how is carbon monoxide formed and what problems does it cause and how to reduce the problem

Answer 5

-its formed from incomplete combustion
-its is very toxic
-you can reduce the problem by using catalytic converters in cars

Question 6

how is carbon particulates formed and what problems does it cause and how to reduce the problem

Answer 6

–its formed from incomplete combustion
-it can cause respiratory problems
-you can reduce the problem by supplying good amount of oxygen when burning fuels

Question 7

how is unburnt hydrocarbons formed and what problems does it cause and how to reduce the problem

Answer 7

-its formed when hydrocarbons arent burned at all
-it causes photochemical smog
-it can be reduced by using a catalytic converter in cars

Question 8

how is NO & NO2 formed and what problems does it cause and how to reduce the problem

Answer 8

-its formed by combustion of N2 gases with O2 in the air at very high temps
-reacts with water to form acid rain
-can be reduced by using a catalytic converter in cars

Question 9

how is sulfur dioxide formed and what problems does it cause and how to reduce the problem

Answer 9

-formed from combustion of sulfur containing compounds
-reacts with water to form acid rain
-it can be reduced by removing SO2 from