Topic 7: Organic Chemistry Flashcards
What is a hydrocarbon?
A molecule made up of only carbon and hydrogen atoms
How is crude oil formed? (6)
1) Microscopic plants obtain energy from photosynthesis
2) Plankton and tiny animals eat the plants
3) Plants and animals die
4) They become buried in sediment unable to decay
5) Layers of sediment increase pressure
6) Over millions of years chemical reactions turn the remains into oil
Where is crude oil found?
Oil rises through permeable sedimentary rock until it reaches an impermeable layer where it is then drilled for
What makes up crude oil?
A mixture of hydrocarbons of different lengths
What are the properties of heavy fractions or long-chain hydrocarbons? (4)
1) High boiling points
2) High viscosity
3) Low volatility (or how quickly it evaporates)
4) Low flammability
What are the properties of light fractions or small-chain hydrocarbons? (4)
1) Low boiling points
2) Low viscosity
3) High volatility (or how quickly it evaporates)
4) High flammability
What are the most common hydrocarbons?
Alkanes
What are alkanes? (3)
1) The simplest hydrocarbons
2) Saturated hydrocarbons where carbon atoms form four single covalent bonds
3) A homologous series
What are saturated hydrocarbons?
Hydrocarbons which only contain single covalent bonds
What is a homologous series?
A group of organic (contains carbon) compounds that react in a similar way
Name the first ten alkanes
Methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane and decane
Why do alkanes make good fuels? (2)
1) They are fairly unreactive but are flammable
2) When completely combusted they release a lot of energy
What is the general formula of an alkane?
CnH2n+2
What forms when hydrocarbons are completely combusted in a plentiful oxygen supply? (2)
1) hydrocarbon + oxygen –> carbon dioxide + water
2) hydrocarbon + oxygen –> lots of energy
What forms when hydrocarbons are completely combusted in a poor oxygen supply?
Carbon monoxide
What are the properties of carbon monoxide?
1) Colourless
2) Odorless
3) Toxic
How is carbon monoxide dangerous?
Carbon monoxide takes oxygen out of the haemoglobin in the blood to become carbon dioxide which means cells do not get enough oxygen
What does breathing carbon monoxide cause? (4)
1) Breathing difficulties
2) Headaches
3) Unconsciousness
4) Death
What is fractional distillation? (2)
1) The process of separating crude oil into groups of hydrocarbons with similar numbers of carbon atoms
2) The separation of a liquid mixture into fractions differing in boiling point
What are the three stages of fractional distillation?
1) Evaporation
2) Condensation
3) Collection
Describe the process of fractional distillation (5)
1) Crude oil is heated until evaporation
2) Crude oil vapour is put into the bottom of a fractionating column
3) The column has a temperature gradient (bottom is hot while top is cool)
4) As the vapour rises, longer hydrocarbons with high boiling points will condense and drain out near the bottom
5) As the vapour rises, shorter hydrocarbons with low boiling points will condense and drain out near the top
Give examples of the end products of fractional distillation (2)
1) Fuel for most modern transport
2) Feedstock for polymers, solvents, lubricants and detergents
What is cracking?
The process where long-chain hydrocarbons are broken down into shorter, more useful molecules
What are the two ways of cracking? (2)
1) Catalytic cracking
2) Steam cracking
