Organic Chemistry Flashcards
Name the first four alkanes and their formulas.
Methane - CH4
Ethane - C2H6
Propane - C3H8
Butane - C4H10
What’s the general formula for alkanes?
CnH2n+2
The shorter the carbon chain the less v________, the more v________ and the more f____________.
viscous, volatile, flammable
What is the word equation for complete combustion?
hydrocarbon + oxygen -> carbon dioxide + water
What are the uses of alkanes?
Fuels.
What is crude oil?
A fossil fuel and a mixture.
What process is used to separate hydrocarbon fractions?
Fractional distillation.
How does fractional distillation work?
- The oil is heated until most of it has turned to gas. The gases enter a fractionating column.
- In the column there is a temperature gradient - hot at the bottom, cooler at the top.
- Longer hydrocarbons have high boiling points. They condense back into liquids and drain out of the column early on when near the bottom. Shorter hydrocarbons have lower boiling points so condense and drain out much later on, near the top of the column.
- The crude oil mixture is seperated into different fractions.
What is a fraction?
A mixture of hydrocarbons that contain a similar number of carbon atoms, so have similar boiling points.
What are the uses of crude oil?
Fuel for transport and the petrochemical industry.
What is cracking?
The splitting up of long-chain hyrdocarbons.
What are the two different methods of cracking?
Catalytic cracking and steam cracking.
Why is cracking needed?
Short-chain hydrocarbons are more flammable so make good fuels and are in high demand.
What are the products of cracking?
An alkane and an alkene.
What is catalytic cracking?
Once the long-chain hydrocarbons have been vapourised, the vapour is passed over hot powdered aluminium oxide (catalyst). The long-chain molecules split apart on the surface of the specks of the catalyst.
What is steam cracking?
Once the long-chain hydrocarbon has been vapourised, they are mixed with steam and then heated to a high temperature.
What is the homologous series?
A group of organic compounds that react in a similar way.
What is meant by saturated compounds?
Each carbon atom forms four single covalent bonds.
What is meant by unsaturated compounds?
They have a double carbon bond.
Are alkenes saturated or unsaturated compounds?
Unsaturated.
What is the general formula for alkenes?
CnH2n
Name the first 4 alkenes.
Ethene C2H4
Propene C3H6
Butene C4H8
Pentene C5H10
In a large supply of oxygen, how do alkenes combust?
Completely, to only produce carbon dioxide and water.
When burned in air, alkenes undergo incomplete combustion, what toxic gases is produced?
Carbon (soot) and carbon monoxide (CO).
Why is carbon monoxide dangerous?
It is poisonous and cannot be seen or smelt. Also known as the silent killer.
What is seen during incomplete combustion?
A smoky yellow flame.
Give the balanced, formula equation for the incomplete combustion of butene.
C4H8 + 5O2 -> 2CO + 2CO2 + 4H2O
What is a functional group?
A group of atoms in a molecule that determines how that molecule typically reacts.
What is the functional group of alkenes?
C=C
What is hydrogenation?
The addition of hydrogen.