Organic Chemistry Flashcards
Explain what alkanes are
-Alkanes are the simplest type of hydrocarbons.
-They are a compounds that react in a similar way
-they are a saturated compounds each carbon atom fours four single covalent bond
First four are :Methane,Ethane,Propane,Butane
How does the length of carbon chain effect the property
The shorter the chain,
-the more runny
-more volatile(meaning it has a lower boiling point),
-more flammable
The length of the hydrocarbon effects it’s use as a fuel . Shorter chains are bottled gases
What is the balanced equation for complete combustion
Hydrogen+oxygen—> carbon dioxide+water
Example
CH4+2O2—>Co2+2H2O
Explain how crude oil can be separated through fractional distillation
-In crude oil there are many different hydrocarbons ,most of them being alkanes
- they can be separated by a fractionating Column where there is a temperature gradient (hot at the the bottom and cooler as it goes up)
-The longer chains of hydrocarbons are condensed into liquid towards the bottom and is drained out through the lower columns because it has a higher boiling point (Bitumen)
- the smaller chains are drained out later on in the column because it has a lower boiling point. (Petrol)
Why do shorter chains of liquids leave the fractionating columns later
Small hydrocarbon molecules have WEAK INTERMOLECULAR FORCES so they have low boiling points. They do not condense, but leave the column as GASES. Long hydrocarbon molecules have stronger intermolecular forces, so they have high boiling points. They leave the column as HOT LIQUID bitumen.
What are the uses of crude oil ?
- Provides file for modern transport ,like cars and planes (kerosene)
- It provides a source for feedstock (raw material used in industrial reactions) for petrochemicals industry
Example : Ethane is an example of a petrochemical used in feedstock to produce polythene (a polymer)
What does homologous series mean?
A family of compound which have the same functional group and chemical properties
Why do alkenes have a double bond?
- They have double bond to show that they have two fewer hydrogen atoms than the corresponding alkane making them unsaturated
- the double c bond open up to form single bonds which bond to other atoms
General formula for alkenes
CnH2n
What is a polymer
A polymer is tiny molecules called monomers(often alkenes) join together
The process is called polymerisation and needs higher pressure and a catalyst
What is the process of cracking?
-Long chains of hydro carbons are Brocken down through cracking since short chains of hydrocarbons are more useful fuels and more flammable
- It is a thermal decomposition reaction through heating
Explain catalytic cracking ?
1.) long chain of hydrocarbon is heated to vaporise them
2.) The vapour is catalysed by hot powdered aluminium oxide
3.) The molecules are split apart
Evaluate the difference between alkene and alkane?
-Alkanes have two more hydrogen atoms then Alkenes
- Alkenes have a double bond making then unsaturated
- Alkenes are more reactive since their double c bond opens up to accommodate other atoms
- Alkenes are more flammable
- Alkenes have a higher boiling point
What are the three addition reactions
Hydrogenation
Alkene + hydrogen —> alkane
Forming alcohols
Alkene + steam —> alcohol (-OH)
Halogenic reaction
Ethene + bromine —> dibromoethane
How can the addition of bromine be tested for Alkenes
1.) If orange bromine water reacts with a saturated compound,like alkanes, it will remain the same
2.) If it reacts with an Alkene,the double bond will cross and the bromine water will loose its colour making a dive-compound
