C9 - Crude Oil and Fuels Flashcards
What is crude oil
crude oil is a mixture of many different carbon compounds. Nearly all of the compounds are hydrocarbons
What is a hydrocarbon
compounds which only contain hydrogen and carbon atoms
What is the problem with crude oil from the ground
It has to many substances with different boiling points so before it can be used it must be separated into different substances with similar boiling points known as fractions
what does distillation do
distillation separates liquids with different boiling points
What is an alkane
saturated hydrocarbons. all the carbon-carbon bonds are single covalent bonds so this means that they contain as many hydrogen atoms as possible in each molecule
what is the general formula for alkanes
CnH(2n+2)
what are the first 4 alkanes
Methane (CH4), Ethane (C2H6), Propane (C3H8) and Butane (C4H10)
Properties of short chain hydrocarbons in comparison to long chain hydrocarbons
Lower Boiling Point
Higher volatility
Very Runny (low viscosity)
Higher Flammability
what is volatility
the tendency to turn to a gas
What is viscosity
how easily it flows
Fractional Distillation process of Crude Oil
Crude oil is heated and get in near the bottom of the fractionating column as hot vapour. The column is kept very hot at the bottom and cooler at the top. Different fractions are collected as liquids at different levels in a continuous process
What gets collected where in the fractional distillation of crude oil?
Hydrocarbons with smallest molecules have lower boiling points so are collected tse d at the cooler top of the column as gases. At the bottom of the column, fractions have higher boiling points and they cool to form very thick liquids or solids at room temperature
Equation for complete combustion of hydrocarbons
Hydrocarbon + Oxygen —> carbon dioxide + water (+energy)
How to test for the gases formed in complete combustion of a hydrocarbon
- Carbon dioxide turns limewater cloudy
- Water turns blue cobalt chlorine paper pink OR white anhydrous copper sulfate blue
What gas is produced in incomplete combustion of hydrocarbons and why is it bad
Carbon monoxide (CO) is formed. It is a toxic gas which is colourless and odourless. Your red blood cells pick up this gas and carry it round your body instead of oxygen
Why are large molecules not good fuels
They are thick liquids/solids with high boiling points. They are difficult to vapourise and don’t burn easily
What fuel for modern transport comes from crude oil
Diesel, Kerosene, heavy fuel oil and LPG
What does cracking involve
Breaking down larger, longer alkane molecules into smaller more useful ones
What is also produced in hydrocarbons cracking
Alkenes which are used as a starting material when making lots of other compounds and can be used to make polymers
What type of reaction is cracking
it is a thermal decomposition reaction as it involves breaking down molecules by heating them
Explain the cracking process (catalytic and steam cracking)
First the long chan hydrocarbon is heated to vaporise it
- CATALYTIC CRACKING - the vapour is passed over a hot powdered aluminium catalyst and the long-chain molecules split apart on the surface of the catalyst
- STEAM CRACKING - the vapour is mixed with steam and heated to a very high temperature
How to test for alkenes or alkanes
Alkenes are generally more reactive than alkanes. A positive test for an alkene is that it reacts with orange bromine water and turns it colourless. Alkanes do not react with bromine water
