What is crude oil ?
- mixture of many different hydrocarbons
- unrefined oil
How is crude oil formed ?
- ancient microorganisms + fossils at bottom of sea pushed down by layers of sediment
- pressure generates heat
- organic matter liquefied
How can specific hydrocarbons be extracted from crude oil in the lab ?
distillation
What is a fraction ?
one substance in crude oil with similar boiling points - these fractions can be further refined once extracted from the whole crude oil.
What is an alkane ?
- saturated hydrocarbon
- has at least one carbon atom
- all carbon to carbon bonds are single covalent bonds
What is the general formula for an alkane ?
C(n)H(2n+2)
Which type of hydrocarbons are the most useful and why ?
- short chain
- ignite well w/clean flames (good for fuel)
- low viscosity (easier to work with)
- volatile (good as solvents)
Describe the fractional distillation of crude oil.
- oil is vaporised before sent into fractionating column
- the bottom of the column is the hottest, and only long chain hydrocarbons liquefy at this point (used for tarmac, roads, etc. - very sticky + thick)
- going up the column, temperature decreases so that the short chain hydrocarbons with very low bps will condense only at the top
going up, fractions are used for:
- tarmac/roads etc.
- diesel/boiler fuel
- kerosene (aircraft fuel)
- petrol/gasoline
- petroleum gas/low bp alkanes (fuels)
What are the products of the complete combustion of a hydrocarbon ?
- water
- carbon dioxide
Describe how to test for the products of complete combustion of a hydrocarbon.
- burn natural gas in bunsen burner
- funnel with air tube to collect vapours
- air tube lead to u-shaped tube surrounded by ice bath with anhydrous copper sulfate at the bottom
- water vapour will condense + turn white powder blue
- CO2 gas continues through to another air tube that’s submerged in limewater
- limewater will fizz to provide positive test for CO2 gas
What are the products of incomplete combustion of hydrocarbons ?
- water
- carbon monoxide
What is cracking ?
- breaking up a long chain hydrocarbon into smaller, more useful hydrocarbons due to the effects of THERMAL DECOMPOSITION
- done by either mixing with steam and heating to an extremely high temperature, or passing the vapours of the hydrocarbon over a hot catalyst
- cracking produces both saturated and unsaturated hydrocarbons
How do you test for an unsaturated hydrocarbon ?
- shake with bromine water
- if the bromine is displaced (water is decolourised), unsaturated hydrocarbon is present
What catalyst can be used in the lab to crack medicinal paraffin ?
broken pot
