Organic chemistry Flashcards
(53 cards)
What is crude oil
crude oil is a finite resource found in rocks. Crude oil is the remains of an ancient biomass consisting of mainly plankton that was buried in mud
What is in crude oil
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 only
what is a hydrocarbon
Molecules made up of hydrogen and carbon only
What is an alkane
Most hydrocarbons in crude oil are alkanes.
Alkanes only contain single covalent bonds and are classed as saturated hydrocarbons
Physical properties of hydrocarbons
- Boiling points and viscosity of hydrocarbons increase as molecules get bigger - because the intermolecular forces become stronger as molecules become bigger
- flammability and volatility of hydrocarbons decrease as molecules get bigger
why does boiling point increase as hydrocarbon molecules get bigger
Inter molecular forces become larger and stronger as the molecules become larger, so more energy is required to break these forces
Complete combustion of hydrocarbons
The combustion of hydrocarbon fuels releases energy. During combustion, the carbon and hydrogen in the fuels are oxidised. The complete combustion of a hydrocarbon produces carbon dioxide and water
What is fractional distillation and what is it used for
Hydrocarbons in crude oil may be separated into fractions, each of which contains molecules with a similar number of carbon atoms by fraction distillation.
These fractions can be processed to produce fuels and feedstock for the petrochemical industry
What is a fraction
A fraction is a group of hydrocarbons in crude oil that have similar chain lengths and boiling points/properties
Uses of alkanes
- solvents: white spirit
- lubricants: grease
- polymers: PVC, polyethene
- detergents: washing powder
How does fractional distillation work
- The crude oil is heated then passed into the bottom of a fractionating column
- The hydrocarbons vaporise and rise up the column, and then cool and condenses into liquid at different levels
- Different hydrocarbons have different boiling points due to the different chain length
- H.Cs with longer chain lengths condense towards the bottom of the column where the temperature is higher
- H.Cs with a smaller chain length rise towards the top of the column and condense where it’s cooler.
- Different fractions condense at different levels
- The tower has a temperature gradient and the temperature of the column decreases upwards
Use of LPG
cooking equipment, heating appliances
uses of petrol
Fuel for vehicles, heats buildings
uses of kerosene
jet fuel
uses of diesel oil
fuel far cars, trains and larger vehicles
uses of heavy fuel oil
large ship engines, marine fuel, power stations
uses of bitumen
used to make tarmac - road making
order and names of fractions in increasing order of size
LPG
Petrol
Kerosene
Diesel oil
Heavy fuel oil
Bitumen
What is cracking
When hydrocarbons are broken down (cracked) into smaller, more useful molecules
what kind of reaction is cracking
thermal decomposition reaction
What does the cracking process involve
Involves heating the hydrocarbons to vaporise them.
The vapours are either:
- passed over a hot catalyst
- or mixed with steam and heated to a very high temperature
Products of cracking
Alkanes and alekenes - unsaturated hydrocarbons ( they have a double C=C bond)
use of cracking products
- High demand for fuels with small molecules and so some of the products of cracking are useful as fuel
- alkenes are used to produce polymers and as starting materials for the production of many other chemicals
Alkenes are more … than alkanes?
alkenes are more reactive
