Organic Chemistry Flashcards
Is crude oil renewable?
No
What is crude oil made up from?
The fossilised remnants of ancient plankton.
What is crude oil a mixture of?
Lots of different compounds that are not chemically combined. Lots of these compounds are hydrocarbons.
What are hydrocarbons?
Molecules made up of only hydrogen and carbon atoms.
What affects the properties of hydrocarbons?
The size of the hydrocarbon.
Where are crude oils found?
In rocks.
What is crude oil used for?
To produce fuels and other important chemicals.
-fuels
-tarmac
What are the most important properties of hydrocarbons?
-flammability
-boiling point
-viscosity
How does the larger size of a hydrocarbon affect its properties?
-less flammable
-higher boiling point
-higher viscosity (i.e. they are thicker and flow less easily)
How many bonds do carbon atoms make?
Four
What type of organic compound is always saturated?
Alkanes
Why are alkanes called saturated hydrocarbons?
Because all their bonds with other atoms are single bonds.
What are some properties of alkanes?
-quite a low reactivity
-combust quite well (burn well)
(this makes the useful as fuels)
What is the general formula for alkanes?
CnH(2n+2)
What are the 4 smallest alkanes?
-Methane (CH4)
-Ethane (C2H6)
-Propane (C3H8)
-Butane (C4H10)
What is an alkane?
A saturated hydrocarbon.
What is fractional distillation?
The process of separating crude oil into groups of hydrocarbons with a similar number of carbon atoms.
What are ‘short-chain hydrocarbons’?
Hydrocarbons with few carbon atoms.
What are ‘long-chain hydrocarbons’?
Hydrocarbons with lots of carbon atoms.
Why does fractional distillation work with hydrocarbons?
Because different-sized hydrocarbons have different boiling points. Fractional distillation separates hydrocarbons using their different boiling points.
Describe the first stage of fractional distillation.
Evaporation- evaporates the crude oil by heating it. Crude oil vapour is put into a fractionating column at the bottom and rises upwards.
Describe the condensing stage of fractional distillation.
The temperature is highest at the bottom of the column. Long-chain hydrocarbons condense at the bottom and are collected as liquids.
Short-chain hydrocarbons have lower boiling points. They pass up the column and condense at lower temperatures nearer the top.
What is the last stage of fractional distillation?
The fractions are collected. They are then processed to create end products.
What are the end products of fractional distillation?
-Fuels (e.g. petrol, diesel) are a common end product
-Petrochemical industry products such as solvents, detergents, and lubricants.
What are homologous series?
Families of similar compounds containing carbon atoms with the same general formula.
What affects the equations for the combustion (burning) of hydrocarbons?
The amount of oxygen that is available.
What happens when you burn hydrocarbons when the oxygen supply is plentiful?
-energy is released
-the oxidation of carbon and hydrogen to create carbon dioxide and water.
What is created when alkanes are burned without enough oxygen?
Carbon monoxide.
2C + 02 –> 2CO
What are the properties of carbon monoxide?
-colourless
-toxic
-odourless
Why don’t heavy fractions of crude oil make good fuels?
They have low volatility.
They have high boiling points.
They don’t ignite easily.
What is cracking?
The process that breaks down long-chain hydrocarbons into shorter-chain molecules that are more useful.
What type of reaction is cracking an example of?
A thermal decomposition reaction.
Describe catalytic cracking.
Vapourised heavy hydrocarbons are passed over the top of a heated catalyst.
Alkanes and alkenes are produced by this reaction.
E.g. hexane –> butane + ethene
Describe steam cracking.
Vapourised heavy hydrocarbons are combined with steam in a high-temperature environment.
Alkanes and alkenes are produced by this reaction.
E.g. decane –> octane + ethene
What type of chemical reactions are involved in cracking?
Thermal decomposition reactions
What are the uses of alkenes?
-Being combined to make polymers
-Starting materials for chemicals like ethanol
What are alkenes?
Hydrocarbons with the functional group C=C.
This means that alkenes have a carbon-carbon double bond.
How reactive are alkenes?
The presence of the C=C functional group means that alkenes have greater reactivity than alkanes.
Why are alkenes unsaturated?
Because they contain a double bond between two of their carbon atoms (C=C). This means that an alkane and alkene with the same length of carbon chain will have different numbers of hydrogen atoms- the alkane will have two more hydrogen atoms.
Which are more reactive alkanes or alkenes?
Alkenes
What are the 4 shortest alkenes?
-Ethene (C2H4)
-Propene (C3H6)
-Butene (C4H8)
-Pentene (C5H10)
What are functional groups?
A collection of atoms that impact the reactions of an organic compound.
What is the functional group of alkenes?
C=C
What is a typical reaction for alkenes?
Addition
How would you test if a substance is an alkene or an alkane?
Mix it with bromine water and shake it. If it’s an alkene it will change colour from orange-brown to colourless.
When a nickel catalyst is present what can be formed?
Alkanes can be formed by combining hydrogen with an alkene.
What is hydrogenation?
Adding hydrogen atoms across a carbon-carbon double bond.
When a phosphoric acid catalyst is present what can be formed?
Alcohols can be formed by reacting alkenes with steam.
What does the homologous series of alcohols have as their general formula?
CnH2n+1OH
What is the functional group of alcohols?
a hydroxyl group (-OH)
What are the 4 smallest alcohols?
-methanol (CH3OH)
-ethanol (CH3CH2OH)
-propanol (CH3CH2CH2OH)
-butanol (CH3CH2CH2CH2OH)
How is ethanol produced by fermentation?
The process of fermentation involves adding yeast to a sugar solution.
What’s the by-product of the fermentation reaction?
Carbon dioxide.
What is the ideal temperature to ferment yeast?
33 degrees
How would you describe the ideal pH for the fermentation of sugar using yeast?
Slightly acidic
What are the ideal oxygen levels for the fermentation of sugar using yeast?
Low levels of oxygen
