7. Organic Chemistry (alkanes, crude oil, combustion) Flashcards
(31 cards)
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)
