Chapter 6 - alkanes Flashcards
Outline some uses for alkanes
Fuels, lubricants, starting materials
Define the term alkane
a saturated hydrocarbon with C-C and C-H single bonds only taking the formula CnH2n+2
What is the main source of alkanes?
Crude oil
What physical properties of alkanes allows them to be separated from a mixture of crude oil?
Different boiling points
Why do branched hydrocarbons have a lower boiling point?
They’re loosely packed so the van der Waals forces aren’t as effective
Define the term fraction
A mixture of hydrocarbons over a particular range of boiling points during fractional distillation
Describe the 3 main stages in fractional distillation
Crude oil is heated and vaporised, the gases enter the bottom of the fractionating column as the gases go up the column the temperature decreases, they condense at different fractions according to their boiling points proportional to the length of hydrocarbon
Explain why long chain alkanes are cracked
To make shorter chain hydrocarbons which are in greater demand therefore more profitable
What are short chain alkanes used for?
camping gas
What are medium chain alkanes used for?
Fuels
What are long chain alkanes used for?
Paraffin
What type of cracking produces a high proportion of alkenes?
Thermal
Outline and describe the catalyst used in cracking
Zeolite, honeycomb structure with enormous surface area
What is the test for alkenes?
Decolorisation of bromine solution
What type of cracking produces a high proportion of branched alkanes and cycloalkanes?
Catalytic
Explain the cause and the effect of carbon monoxide
Incomplete combustion, it’s poisonous and it increases asthma/ breathing problems
Outline the cause and effect of nitrogen oxides
High temperature engine –> acid rain and smog
Outline the cause and effect of sulphur dioxide and suggest how it could be treated
Sulphur impurities in fuels –> acid rain, removed with limestone/ calcium oxide (neutralisation)
Explain why CO2 is bad for the atmosphere
It’s a greenhouse gas and therefore contributes to global warming
What catalyst is used in a catalytic converter?
Platinum
What are catalytic converters used for?
Removal of carbon monoxide, unburnt hydrocarbons and nitrogen oxides
Explain the structure of the catalyst in the catalytic converter
The platinum is coated on a ceramic honeycomb to reduce cost and increase surface area
