Organic - 3.2 Alkanes Flashcards
What is a catalytic converter?
A device fitted in a car to reduce the amount of emissions from an internal combustion engine.
What is catalytic cracking?
A type of cracking that takes place at a slight pressure, high temperature and in the presence of a zeolite catalyst and is used mainly to produce motor fuels and aromatic hydrocarbons.
What is cracking?
A process which involves breaking C-C bonds in alkanes to produce shorter chained alkanes and alkenes.
What is fractional distillation?
A method of separating mixture of substances according to the different boiling points. Common used to separate crude oil into different fractions.
What are hydrocarbons?
Compounds made up of carbon and hydrogen atoms only
What does saturated mean?
Organic compounds are saturated if all the carbon-carbon bonds are single C-C bonds. Alkanes are saturated hydrocarbons.
What is thermal cracking?
A type of cracking that takes place a high pressure and high temperature and produces a high percentage of alkenes.
What is the general formula of alkanes?
CnH2n+2
State the first four alkanes
Methane ethane propane butane
Are alkanes polar and why?
No, because the difference in electronegativity between the carbon atom and hydrogen atom is very small
How are mixtures of alkanes separated?
Through fractional distillation
What is fractional distillation?
The continual evaporation and condensation of a mixture causing the components to separate because of a difference in their boiling points
What is a fraction?
A group of compounds that have similar boiling points and are removed at the same level of a fractionating column
Is a fractionating column hotter at the top or bottom?
Hot at the bottom and cool at the top
What is cracking?
A process where long chain hydrocarbon molecules are broken into shorter chain molecules that are in high demand
What happens in thermal cracking?
Long chain alkanes are heated to a very high temperature high-pressure and in a short time this produces shorter alkanes and rich in alkenes.
What happens in catalytic cracking?
Long chain alkanes are heated under pressure with a zeolite catalyst
What are the conditions and products of thermal cracking?
Temperature = 1000-1200K
Pressure = 700atm
Time = one sec
Catalyst = none
Products = high percentage of alkanes and short chain alkanes
What are the conditions and products of catalytic cracking?
Temperature = 800-1000 K
Pressure = 1-2atm
Time = 2-4secs
catalyst = zeolite
Products = aromatic hydrocarbons and motor fuels
Describe the complete combustion of alkanes
Alkanes burn in oxygen to produce carbon dioxide and water only
Describe the incomplete combustion of alkanes
Alkanes will burn for water and carbon monoxide, which is toxic
What is a catalytic converter?
Reduces the amount of carbon monoxide and nitrous oxide and unburnt hydrocarbons by converting them into less toxic gases
Describe the process that occurs in an internal combustion engine
A small amount of fuel and excess air enters the combustion chamber.
The mixture is then compressed and ignited with a temperature spark .
Mixture then burns explosively forcing movement of the engine.
The products exit via the exhaust
Why can sulphur dioxide be removed from flue gases by calcium oxide and calcium carbonate?
They neutralise the acidic sulphur oxide to form calcium sulphate which is used for construction