Organic Chemistry Flashcards
2
What is a hydrocarbon?
it is a compound made up of only hydrogen and carbon atoms
What is the alkane formula?
CnH2n+2
What is a homologous series?
a group of organic compounds that react in similar ways
What are alkanes?
they are fully saturated hydrocarbons that are a homologous series.
What is a saturated compound/hydrocarbon?
it has the maximum amount of single bonds (carbon is fully saturated in a hydrocarbon when it makes 4 bonds, ie max amount of bonds)
What are the first 5 alkanes called?
Methane, Ethane, Propane, Butane, Pentane
Draw methane and propane as displayed formula.
Methane: CC - H - C CPropane: C C C C - H - H - H - C C C C
How do the properties of Hydrocarbons change as the length of the carbon chain changes?
The longer the chain, the more viscous it isThe longer the chain, the less volatile it is (higher boiling points as length continues)The longer the chain, the less flammable it isAffects how they are used for fuels.
How does the length of a hydrocarbon affect how they are used in fuels?
Short hydrocarbons with lower boiling points are used as ‘bottled gases’, stored under pressure as liquid in bottles.
What is the equation for complete combustion?
Hydrocarbon + oxygen -> carbon dioxide + water (+ energy)
What is oxidation?
the gain of oxygen, loss of electrons
During complete combustion what happens to the hydrocarbon?
Both the hydrogen and carbon from the hydrocarbon are oxidised
Why are hydrocarbons used/good as fuels?
Due to the high amount of energy they release when they completely combust
Write the balanced equation for the complete combustion of methane (CH4)
CH4 + 2O2 -> CO2 + 2H2O
What is fractional distillation?
it is a process which can be used to seperate Hydrocarbon fractions.
What is crude oil?definition
It is a fossil fuel, formed over millions of years due to high temp and pressure.
Are fossil fuels renewable/ infinite resources?
No. Fuels like coal, oil and gas are are non-renewable fuels which are non-finite
What is crude oil?in terms of hydrocarbons
It is a mixture of lots of different hydrocarbons, which are mainly alkanes.
What is the process of fractional distillation?
- The oil is heated until most of it has evaporated into gas- the gases enter the fractioning column- In the column there is a temperature gradient (hot at the bottom, colder as you go up)-Longer hydrocarbons have higher boiling points, so as the gases rise up the column, they condense back to a liquid at a lower point than shorter hydrocarbons, which condense at the top of the column- the crude oil is now separated into different fractions, which all have a similar amount of carbon atoms thus why they have a similar boiling point.
Why do some hydrocarbons condense earlier in the fractioning column?
they have higher boiling points, so they condense when the temperature becomes too low as they rise up as a gas. This is because of the high amount of carbon atoms they have, giving them a higher boiling point.
What are some uses of crude oil?
- oil for fuel for transport- lubricants, polymers, solvents
What is cracking?
Its the splitting up of long hydrocarbon chains to make them into shorter, more valuable chains.
Why are short hydrocarbon chains good fuels?
They are flammable so combust fully more easily, therefore are also in high demand.
What are some benefits to cracking?
- create more in demand, valuable short hydrocarbon chains- use up the less useful long chain hydrocarbons
What is the cracking equation?
Long chain hydrocarbon -> shorter chain hydrocarbon (alkAne) + an alkEne
What type of reaction is cracking?
it is a thermal decomposition reaction, which breaks down molecules by heating them up
What are the types of cracking?
Steam cracking and catalytic cracking
What is catalytic cracking?
- heat long chain hydrocarbons to vaporise them (turn to gas)- pass the vapour over a hot powdered aluminium oxide catalyst- the long chain hydrocarbon splits on the catalyst
What is steam cracking?
-vaporise the hydrocarbons, mis them with steam- heat them to a very high temperature
What are alkenes?
They are unsaturated hydrocarbons in a homologous series. They have 2 less hydrogens than a alkane due to their double bond ( C=C)