7. Organic Chemistry (alkanes, crude oil, combustion) Flashcards
What is a hydrocarbon?
A compound made exclusively of hydrogen and carbon atoms
What are alkanes?
Saturated hydrocarbons with a general formula of CnH2n+2
What is a homologous series?
A series of organic compounds that have similar chemical properties, due to them having the same functional group
What does 1 carbon begin with?
meth-
What does 2 carbons begin with?
eth-
What does 3 carbons begin with?
prop-
What does 4 carbons begin with?
but-
Why can 1 carbon atom bond 4 times?
because it has 4 electrons on its outermost shell
Why are alkanes called saturated hydrocarbons?
because they are made up of single carbon-carbon covalent bonds
What is crude oil?
- A mixture of hydrocarbons with different boiling points
- a finite resource found in rocks
What does incomplete combustion of hydrocarbons produce?
- carbon monoxide and water
- less energy than complete combustion
Describe the physical properties of alkanes?
- first few in series are gases, then change to liquids, then to solids
- in general, boiling points and viscosity increase as molecules get bigger
- volatility and flammability decrease as molecules get bigger
- poor reactivity
What is combustion and what kind of reaction is it?
- burning of fuels
- an oxidation reaction, hence an exothermic reaction
What is the equation for the complete combustion of hydrocarbons?
hydrocarbon + oxygen —> carbon dioxide and water
Explain how fractional distillation of crude oil takes place
- Crude oil is heated and vapourised
- The vapours rise up the fractional column
- The column is hotter at the bottom, and cooler at the top
- Hydrocarbons cool as they go up the column and condense at different heights, as they have different boiling points
- large molecules with high boiling points are collected at the bottom
- small molecules with low boiling points are collected at the top
- The liquid hydrocarbons then collect in trays and drain out, giving fractions which can be processed to produce fuels and feedstock for the petrochemical industry.
How is crude oil formed?
- Crude oil is formed from the remains of dead plants and animals, particularly plankton
- These organic remains were covered by mud and sand, and buried in the Earth
- Over millions of years, these organic remains were compressed under a lot of heat and pressure
- The heat and pressure chemically changed the organic remains into crude oil
What are the properties of short chain hydrocarbons?
- lower boiling points because there are fewer bonds to break
- high volatility because of fewer bonds
- low viscosity
- high flammability
What do the properties of hydrocarbons depend on?
the length of carbon chains
What is volatility?
the tendency of a substance to turn into a gas
What is viscosity?
how thick a substance is/how easily a substance flows
What are the properties of long chain hydrocarbons?
- higher boiling points because there are more bonds to break
- low volatility because there are more bonds
- high viscosity
- low flammability
What three things, in order, at produced towards the middle of the fractional column from crude oil?
- Petrol
- Kerosene
- Diesel
What two things, in order, at produced at the bottom of the fractional column from crude oil?
- Heavy fuel oil
- Bitumen
What is produced at the top of the fractional column from crude oil?
Liquified Petroleum Gas (LPG)
Why are short chain hydrocarbons higher in demand?
They make good fuels due to high flammability
Where is crude oil found?
In rocks
Which 3 hydrocarbons are used as fuel?
- petrol
- kerosene
- diesel
What is feedstock?
A raw material used to provide reactants for an industrial reaction (the different hydrocarbons in crude oil)
What are petrochemicals?
A substance made from crude oil via chemical reactions (polymers, solvents, lubricants)
Which hydrocarbon makes up most of the hydrocarbons in crude oil?
alkanes
What useful materials, on which modern life depends on, are produced by the petrochemical industry?
- solvents
- lubricants
- polymers
- detergents