topic 7 - organic chemistry Flashcards
what is crude oil?
- crude oil is a finite resource found in rocks.
- crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud
what is crude oil a mixture of?
- crude oil is a mixture of a very large number of compounds
- most of the compounds in crude oil are hydrocarbons, which are molecules made up of hydrogen and carbon atoms only
what is the general formula for the homologous series of alkanes?
CnH2n+2
what are the first four members of the alkanes?
- methane
- ethane
- propane
- butane
what is viscosity?
- the thickness of a fluid
- fluids with a high viscosity flow slowly
what occurs as the size of the hydrocarbon molecules increases?
- as the size of the hydrocarbon molecules increases, the molecules get more viscous
what is the flammability of hydrocarbons?
- short-chain hydrocarbons are extremely flammable
- as the size of the hydrocarbon molecules increase, the molecules get less flammable
- so long-chain hydrocarbons are very difficult to burn
what is the boiling point?
- the temperature at which a liquid turns to a gas
what are the boiling points of hydrocarbons?
- short-chain hydrocarbons have low boiling points
- as the size of the hydrocarbon molecules increases, the boiling points also increases
- very long chain hydrocarbons have very high boiling points
what is the state of hydrocarbons at room temperature?
- gases
- their boiling points are lower than room temperature
what do hydrocarbon fuels release when combusted?
- energy
what occurs during the combustion of hydrocarbon fuels?
- during combustion, the carbon and hydrogen atoms in the fuel react with oxygen
- the carbon and hydrogen are oxidised
- if the oxygen is unlimited, this reaction produces carbon dioxide and water
what is the word equation for the complete combustion of methane?
methane + oxygen -> carbon dioxide + water
how does fractional distillation of crude oil take place?
- crude oil is heated and vaporised
- vapor rises up to the fractionating column
- the column is hotter at the bottom and cooler at the top
- hydrocarbons cool as they go up the column 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, high boiling points - collected at the bottom
- small molecules, low boiling points - collected at the top
- this gives fractions which can be used in various ways
what are examples of fractions used as fuels?
- petrol and diesel
- kerosene
- heavy fuel oil
- liquified petroleum gas
what is feedstock?
- a feedstock is a chemical that is used to make other chemicals
what are examples of feedstock?
- solvents
- lubricants
- detergents
- polymers
what is cracking?
hydrocarbons being broken down to produce smaller, more useful molecules
what type of reaction is cracking?
- thermal decomposition
what is catalytic cracking?
- in catalytic cracking, we use high temperatures and a catalyst
what is steam cracking?
- in steam cracking we use high temperature and steam
what are alkenes used to make?
- polymers
which is more reactive: alkanes or alkenes?
alkenes
how do you test for alkenes?
- we test for alkenes using bromine water, which is orange
- if shaken with alkene, then the bromine water becomes colourless
what is the general formula for alkenes?
CnH2n
why are alkenes unsaturated?
- they contain 2 fewer hydrogen atoms than the alkane with the same number of carbon atoms
what are the names and formulae of the first 4 members of the homologous series of alkenes?
- ethene (C2H4)
- propene (C3H6)
- butene (C4H8)
- pentene (C5H10)
what is the functional group for alkenes?
C = C