C6.2 - Organic chemistry Flashcards
What are there features of Alkanes?
They have :
- 4 bonds ( the maximum number a carbon atom can make )
- single bonds ONLY
What are Alkanes ?
Alkanes are a homologous series of saturated hydrocarbons with the general formula of C nH 2n+2
what does saturated mean ?
that something contains single bonds only
what does unsaturated mean ?
that something contains double bonds only
what is a hydrocarbon ?
something that contains hydrogen and carbon atoms only
what is a homologous series?
A homologous series has the same general formula and have similar chemical properties
what is viscosity ?
the strength of intermolecular forces
how does the size of alkanes effect their properties ?
As the size of an alkane increases, its boiling point and melting point increase, as do its viscosity and density
Name the features of small Alkanes ?
- low boiling points
- High flammability
- Clean cleanliness of flame
- Low viscosity
Name the features of large Alkanes ?
- High boiling points
- Low flammability
- Sooty cleanliness of flame
- High viscosity
What are the uses of Alkanes ?
1 ) As fuels
2 ) For Cracking
When does complete and incomplete combustion occur + formulae ?
Complete - in a good supply of oxygen –> COv2 + Hv2O
Incomplete - in a poor/ limited supply of oxygen –> CO or C + Hv2O
Explain how Alkanes are used for fuels?
Alkanes burn well, releasing a lot of heat energy, eg :
Complete combustion : CHv4 + 2Ov2 —> COv2 + Hv2O
Incomplete combustion : CHv4 + 1½Ov2 —> CO + 2Hv2O
THIS IS BALANCED
Explain how Alkanes are used for cracking?
long alkanes —> short alkanes + alkene
short alkanes are used as fuels
alkenes are used to make polymers
How can we balance combustion equations?
Using the CHO method:
balance carbon atoms first, hydrogen atoms second and lastly oxygen atoms
Name the Alkanes based on the number of carbons?
1 - methane
2 - ethane
3 - propane
4 - butane
Draw the displayed formula of the displayed formula of alkanes ( methane , ethane, propane, butane and pentane )
What are alcohols ?
Alcohol’s are the homologous series containing the functional group - O - H
Name the alcohols based on the number of carbons?
1 - methanol
2 - ethanol
3 - propanol
4 - butanol
What is the general formula for alcohol’s ?
Cvn Hv2n+1 OH
Draw the displayed formula of alcohols ( methanol , ethanol, propanol, butanol and pentanol )
What are the uses of alcohols?
- Fuels
- Solvents
- Ethanol in ALCOHOLIC drinks
Explain how Alcohols are used for fuels?
Like alkanes they burn in oxygen ( or air ):
Complete combustion : Cv2Hv5OH + 3Ov2 —> 2COv2 + 3Hv2O ( producing water vapour and carbon dioxide )
Incomplete combustion : Cv2Hv5OH + 2Ov2 —> 2CO + 3Hv2O ( producing carbon monoxide and water vapour )
Explain why Alcohols are used for solvents?
Since they have low boiling points and are therefore volatile ( easily vaporises )
What are the dangers of using ethanol in ALCOHOLIC DRINKS ?
all alcohols are toxic so if there is too much ethanol in a space of time = it can result in death
What are Alkenes ?
Alkenes are a homologous series of unsaturated ( contains double carbon bond ) hydrocarbons with the general formula C nH 2n
What is the general formula of Alkenes?
C nH 2n
Name the alkenes based on the number of carbons?
2 - ethene
3 - propene
4 - butene
5 - pentene
Draw the displayed formula of Alkenes ( ethene, propene, butene, pentene )
What are the rules of displayed formula for Alkenes?
- C=C per Alkene
- C has max 4 bonds
Name features of Alkenes in reactions ?
- Alkenes are very reactive ( due to presence of the C=C double bond which undergoes addition reactions
- In addition reactions, the C=C double bond becomes a C-C single bond and other atoms join onto the two C atoms
- Alkenes do also burn, but they are rarely burned as they are ( a ) too valuable for making polymers and ( b) tend to undergo incomplete combustion with smoky flame
How can double C=C bonds in Alkenes be tested?
By testing it with Bromine water =
Bromine is only orange when bonded to another Bromide atom since it’s diatomic. When an Alkene reacts with Bromine water it turns from orange to colourless proving that Alkenes react and decolourise Bromine water proving the existence of a C=C bond, a part of an alkene.
Look at Alkenes and how to draw them when they react with something else?
OK
What do Alkenes need to react with to make Alkanes and Alcohols?
Alkanes = at 150o with nickel catalyst ) - Hv2\
Alcohols = ( at high temp with concentrated phosphoric acid catalyst ) Hv2O