Organic Chemistry Flashcards
What is a hydrocarbon
Compound that is formed from only carbon and hydrogen atoms
What is an alkane
Simplest type of hydrocarbon you can get with a genral formula of: CnH2n+2n
Part of the homologous series
Saturated compounds - carbon atom with 4 single covalent bonds
Properties of hydrocarbons as it gets longer
Longer the chain the more viscous it is (gloopy)
Longer the chain the less volatile it is (high melting point)
Longer the chain the less flammable it is
Equation of complete combustion
Hydrocarbon + oxygen —> carbon dioxide + water (+energy)
Why are hydrocarbons used as fuel
The amount of energy released when they combust completely
How is crude oil formed
Formed from remains of animal and plant matter (mainly plakton)- that has been heated and pressurised over millions of years
What is a non-renwable resource
Coal,oil,gas are non-renewable resources that are being used more then they are formed -finite
How does fractional distillation work
1) crude oil enters as a liquid into the fractionating column and turns into a gas due to the high temperatures
2) Its hotter at the bottom so long chain hydrocarbons with greater melting point condenses into a liquid and is drained out
3) Shorter chain hydrocarbons float yp until it is cool enough for it to condense into a liquid and drain out
4) crude oil eventually seperated into different fractions
Name the different types of fuels from least boiling point to greatest
LPG
Petrol
Kerosene
Diesel oil
Heavy fuel oil
Bitumen
Crude oil uses in modern life
Used for modern transport-cars,trains and planes (disel oil, heavy fuel oil and kerosene)
Crude oil used as feedstoxk to make new compounds dor use in things like polymers,solvents and lubricants and detergents
What is cracking and why are hydrocarbons cracked
Short chain hydrocarbons are flammable so make good fuels and are in high demand -unlike long chain hydrocarbons.
Long chsin hydroxarbons cracked to reduce the demsnd for short chsin hydrocarbons
Alkenes are also produced which are more reactive than alkanes - used as a starting material for polymers
Test for alkenes
1) orange bromine water added to an alkane, no reaction happens and it stays bright orange
2) If its added to an alkene the bromine reacts to create a colourless compound - colourless solution
How to crack hydrocarbons
Catalytic cracking
Steam cracking
Thermal decomposition reaction- breaking molecules by heating them
1) first step is to heat long chain hydrocarbons
vapour passed over hot powdered aluminium oxide catalyst
Long chain molecules split apart on the surface of the speck sof catalyst- catalytic cracking
2) vaporise hydrocarbons and mix them with steam at a very high temperature -steam cracking
Name the four first alkanes
Ethane,methane,propane,butane
Give an equation of cracking a long chain hydrocarbon
Long chain molecule. —> short chain molecule + alkene
C10H22———-> C8 + C2H4
Decane —–> Octane + ethene
