Organic Chemistry Flashcards
What is a hydrocarbon?
Any compound that contains carbon and hydrogen only
What is an alkanes?
Alkanes are the simplest type of hydrocarbon you can get. They are a homologous series - a group of organic compounds that react in the same way. Each carbon atom forms four single covalent bonds.
What is the general formular for alkanes?
CnH2n+2
What are the first four alkanes?
Methane
Ethane
Propane
Butane
What are the properties of alkanes?
The shorter the carbon chain the more runny the hydrocarbon is - less viscous. They are also more volatile i.e lower boiling points. The shorter they are the more flammable.
Give a uses of hydrocarbons with small chains of carbon
Bottled gas - short chains
What is the reaction of complete combustion of a hydrocarbon?
hydrocarbon+oxygen->carbon dioxide+water
The carbon and hydrogen are both oxidised.
What is the balanced equation for complete combustion of a hydrocarbon?
CH4 + 2O2 -> CO2+2H2O
What is crude oil?
Crude oil is a fossil fuel, it is the remains of dead plants and animals mainly plankton - over millions of years high pressure and temperature turned the remains into crude oil. It is a non renewable energy source as it is finite.
What is fractional distillation?
This is how crude oil is separated by fractional distillation.
The oil is heated until most of it has turned into gas. The gases enter the fractionating column.
In the column there’s a temperature gradient
The longer hydrocarbons have high boiling points.
They condense condense back into liquids and drain out of the column early on, when they are near the bottom.
The shorter hydrocarbons have lower boiling points. They condense and drain out much later on much later on, near to the top where it is cooler.
What is crude oils various uses?
Oil provides the fuel for most modern transport
Feed stock to make new compounds for use in things like polymers,solvents,lubricants and detergents
Organic compounds
What is cracking?
It is the process of making alkanes made by fractional distillation smaller and more useful. It is also used to produce alkenes these are used for starting materials when making polymers
Give the process of cracking
Cracking is a thermal decomposition reaction
The first step is to heat long-chain hydrocarbons to vaporise them (turn them into gas)
The vapour is passed over a hot aluminium oxide catalyst
The long chain molecules split apart on the surface of the specks of catalyst - this is catalytic cracking.
You can also crack hydrocarbons by mixing it with steam then heating.
A long-chain hydrocarbon molecule will turn into a shorter alkane and alkene.
What are Alkenes?
Alkenes are hydrocarbons with a double bond between two of the carbons atoms in their chain. Alkenes have two fewer hydrogen’s but the same amount of carbon making them unsaturated. Alkenes are reactive as this double bond can break allowing the two carbons to bond with the other atoms. The first four alkenes are ethene (with two carbon atoms) propene (three C’s), butene (four C’s) and pentene (five C’s).
What is the general formula for alkenes?
CnH2n
What is the formula for an alkene going through incomplete combustion?
alkene+oxygen=>carbon+carbon monoxide+water+energy
How can you tell when there is incomplete combustion with an alkene?
There is a smoky yellow flame, and less energy is being released.
What is the symbol equation for this?
C4H8+5O2=>2CO+2CO2+4H2O
What is a functional group?
Is a group of atoms in a molecule that determine how that molecule typically reacts.
How does hydrogen react with an alkene?
The addition of hydrogen is known as hydrogenation, hydrogen can react with the double bonded carbons to open up and become saturated.
What is crude oil?
It is a finite resource made from plankton remains over millions of years it is found in rocks. Crude oil is a mixture of hydrocarbons.
Give properties of alkanes
They are saturated molecules
The carbon atoms are fully bonded
Give properties of the alkane group
As the size of the hydrocarbon increases the molecules get more viscous
The shorter the chain of hydrocarbon the more flammable.
The longer the hydrocarbon the higher the boiling point
How are hydrocarbons used as fuels?
Hydrocarbon fuels release energy when burned. During the combustion the carbon and hydrogen atoms react with oxygen and oxidise. If the oxygen is unlimited there will be complete combustion and the products will be CO2 and water.
Why do we use fractional distillation for crude oils?
So they are more useful - fuels such as kerosene, heavy fuel oil and liquefied petroleum gas