topic 7:organic chemistry Flashcards
What is crude oil?
crude oil is a mixture of compound; fossil fuel consisting of the remains of ancient biomass
Finite resource – cannot be replaced as it is used up
What is a hydrocarbon?
A compound made up exclusively of hydrogen and carbon atoms
What are alkanes?
saturated hydrocarbons of a general formula C n H 2n+2
What is a homologous series?
Series of compounds with the same general formula, same functional groups and similar chemical properties
describe the combustion of hydrocarbons
Exothermic reaction occurring when hydrocarbons are reacted with oxygen
Complete combustion produces carbon dioxide and water (carbon and hydrogen atoms are completely oxidised)
Incomplete combustion produces carbon or carbon monoxide and water
Describe the physical properties of alkanes
first few in series are gases, then change to liquids then to solids
In general boiling points and viscosity increases as molecules get bigger
volatility and flammability decrease as molecules get bigger
poor Reactivity
explain how fractional distillation of crude oil takes place
-Crude oil is heated and vaporised
-Vapour rises up the fractionating column
-The column is hotter at the bottom and cooler at the top
-Hydrocarbons as they go up the column and condensed at different height, as they have different boiling points
-Large molecules, high boiling points-collected at the bottom
-Small molecules, low boiling points-collected at the top
-This gives fractions, which can be used in various ways
what is cracking
When large hydrocarbons are thermally broken down into smaller and useful molecules
What type of reaction is cracking?
Thermal decomposition
what are the conditions for cracking
Reactant heated to vapour, passed over a hot catalyst or heated to vapour, mixed with steam and heated to high temperatures
How are the products of cracking used?
The products are alkanes and alkenes -used as polymers and starting materials for synthesis
what is an alkene?
Unsaturated hydrocarbon. Contains a C=C bond
General formula for Alkenes is :CnH2n
what is the test for alkenes
Add bromine water. Colour changes occur from orange to colourless.
describe the combustion of alkenes
They burn with smoky flames due to incomplete combustion
describe addition reactions of alkenes
addition atoms across the carbon – carbon double bond so that the double bomb becomes a single carbon – carbon bond
a) with hydrogen-hydro generation; requires a high temperature and a nickel catalyst
b) with steam-hydration; requires high temperature, pressure and concentrated phosphoric acid as a catalyst
c)with Br2/Cl2/I2
What is an alcohol?
an organic compound that contains an - OH functional group
State characteristics of methanol, ethanol,propanol and butanol
-Dissolve in water to form a neutral solution
-React with sodium to form hydrogen
-Burn in oxygen
-react with carboxylic acid in presence of acid catalyst to form Esther
Oxidation of the alcohol leads to
carboxylic acids
What are some uses of alcohols?
fuels,solvents,drinks
State the conditions required for fermentation of glucose and state the equation of the reaction
30°C, aqueous solution of the glucose, absence of air, yeast added
C6H12O6 —-> 2 CH3 CH2 OH + 2CO2
what are carboxylic acids
organic compounds that contain a COOH functional group
State characteristics of carboxylic acids
-Dissolve in water to form an acidic solution(contains H+ ions)
-React with metal carbonates to form carbon dioxide
-React with alcohol within an acid catalyst produce Esters
-React with metals to give off hydrogen gas
what type of acid is carboxylic ackd
it is a weak acid
Explain my carboxylic acids are weak acids
they are partially dissociated in water, thus the pH of carboxylic acid in solution is not as low as a solution of a strong acid of the same concentration
what is an ester and how is it formed
an organic compound containing a -COO- functional group, formed from carboxylic acid and alcohol in the presence of sulphuric acid catalyst
They have a fruity smell
what is a polymer? How do molecules containing a C=C bond form polymer
A polymer is a longchain molecule which is made by lots of smaller molecules joining together
C=C bond and many smaller molecules joined together to form a chain. No other products are made.
It is called an (addition polymerisation) reaction
give free examples of addition polymers and their uses
Polythene-plastic bags
What is a repeating unit of a polymer?
it is a smallest structure which upon numerous translation, yields the structure of the polymer
In addition polymers: to draw it, take a monomer, change C=C to C-C and additional single bonds extending away from these carbons
akene + water
alkanes
-hydrogenation
alkenes+water
alcohol
-hydration
alkenes + halogen
haloalkane
what happens if you react alcohol with
-sodium
-oxygen
-water
sodium-fizzes
oxygen-burns
water-dissolves
equation for fermentation
sugar ——> ethanol + carbon dioxide
yeast 37
what happens if you react carboxylic acid
-carbonates
-alcohols
carbonates-fizzes
alcohols-esters
make ethene a polymer
| | n C=C | | h h
break the carbon double bond
[-C-C-]
add brackets with n outside
what’s the diffrence between a poly ethene displayed formula and polypropene
C=C.
has CH3 in the corner
How can large hydrocarbons molecules be cracked in an oil refinery?
A heavy fraction distilled from crude oil is heated to vaporise the heat hydrocarbons the vapour is then
passed over hot catalyst
or mix with steam and heated a very high temperature 
what type of reaction is cracking an example of?
Thermal decomposition
why is crude oil not very useful as a product itself?
There are too many substances with all different boiling points
Why are alkanes described as saturated hydrocarbons?
They contain as much hydrocarbon atoms as possible
Name the products of the complete combustion of a hydrocarbon
carbon dioxide + water
describe a positive test for each of the products of combustion
White anhydrous copper sulphate with water and the white powder turns blue
explain the steps involved in the fractional distillation of crude oil
 crude oil is separated into hydrocarbons with similar boiling points called fractions
Each hydrocarbon fraction contains molecules with similar number of carbon atoms each of these fractions boil at different temperature range because of the different sizes of molecules in it
Is heated and fed bottom of the tall tower as hot vapour. The column is kept very hot at the bottom much cooler than the top to the temperate decreases going up the column.
how do the size of a hydrocarbon molecule affect?
The boiling point
The volatility
The viscosity of a hydrocarbon
boiling point -increases
volatility-decreases
viscosity-increase
flammability-decreases
